Design a mobile app that allows ‘users’ to easily buy and sell used books.

Venkatesh Gupta
Aug 17, 2019 · 11 min read

The Challenge

Design a mobile app that allows ‘users’ to easily buy and sell used books.

Expected approach:

  1. Define facts like what is the scope of the app, who would be the audience etc. If you are not certain of some facts, you’ll need to make a few assumptions on your own and make a solution accordingly.
  2. Break down the problem into parts (Define the different types of users, what actions can a user take and what this would result in).
  3. Think of an end to end solution for different kind of possible users for this app. Think about what elements you think should be there on any given app screen and what would be the user journey.
    Hint: You may use a pencil and paper to make app screens (Wireframing) & to make user flows.

Expected output:

  1. Documenting the problem & a well thought through the detailed solution (assumptions, facts, and your thought process)
  2. Screens & Information architecture (What options will be shown where, how will one screen be linked to the other)
  3. User flows for different scenarios and user types

Please note that detailed mockups are not required (though you may use if it helps). You should just be able to do a good job of depicting the information architecture and user flows.

Your assignment would be assessed based on -

1) Thoughtfulness — how clearly you have thought the solution through

2) Analytical and structured thinking

My Approach

I would like to divide the problem into 4 parts:-

  1. Talking to Users.
  2. Tradeoffs from Business Perspective.
  3. Analyzing Competitors.
  4. Designing UX for the app.

Part 1:- Talking to Users

A. Conducting Interviews

To start with this design challenge, I interviewed some of my family members and friends who are studying in schools, colleges, preparing for competitive examinations or are bibliophiles (people who love owning and reading books). Interviewing them I came to know:-

  • How often do they buy a book?
  • Do they prefer buying new or old books?
  • From where do they buy these books? Do they prefer to buy books online or at brick and mortar locations?
  • How much money do they spend on buying books in a year?
  • What are the alternatives to buying a book?
  • What other factors play a role when they buy a book?
  • What do they do with their used books?
  • What is that one thing they hate and love the most while buying and selling books?

Interviewing them, helped me to understand their concerns and pain points, and gave me relevant information to proceed to the next step.

B. Affinity Mapping

After interviewing them, of the points I noted, I started to put them on sticky notes. This helped me to group the alike ideas/concerns together and identify recurrent themes and major pain points.

What do you do when you need a book?

What do you do with the used book?

C. Possible User Actions

  1. Buy
  2. Sell
  3. Donate
  4. Rent
  5. Exchange
  6. Request

For the simplicity of the problem and considering the scope of the question — I’m limiting user action to onlyBuy and Sell Used Books.

D. User Personas

After doing affinity mapping and interviewing people, I have come up with 5 types of users who will be using the app.

User Persona 1
User Persona 2
User Persona 3
User Persona 4
User Persona 5

2. Tradeoffs from the business perspective

After interviewing users, affinity mapping, defining user actions, creating personas and defining their pain points, I would want to analyze which model would best suit the app for buying and selling used books.

Which model best suits best from a business perspective?

A. Inventory Led Model

Red arrows represent the buying cycle whereas Blue represents the selling cycle.

In the Inventory based model,

  • Our platform would have its own inventory where pools of books would be held. When a buyer scroll-throughs the books on the app, he can make a purchasing decision and place an order, subject to availability in the warehouse.
  • The seller (individual or old book stores) can sell the books on the app by uploading all relevant details like book name, publisher name, image, condition, etc. The seller can request a pickup or submit the book at brick and mortar location. On a stringent quality check, a deal is made between the two and the book is added to the warehouse.

Let’s evaluate the inventory-based model,


  • Inventory Based Model helps in having full control of every step of the order cycle.
  • Ensuring Quality Check and Delivering The Trust Right:- The biggest problem in the used book space is that a buyer is always concerned about the quality of the books. Imagine, you are reading an amazing novel, 65 pages later, you find 5 pages missing. The pain with the trust issue of the old books and the brand delivering it hits a low. While collecting books from sellers; a quality check can ensure that only books in good conditions are added to inventory.
  • Seamless delivery process:- The delivery process is seamless as only one entity is involved in the entire process.


  • Warehouse Cost /Inventory Holding Cost — How many warehouses are needed to serve the entire country? Fewer warehouses would mean more logistic costs. Setting up /renting warehouses needs huge CAPEX costs.
  • Huge Resource in collecting used books for sale — When a person marks a book for sale; it needs to be collected at a certain brick and mortar location or a delivery agent. This point of contact needs to check the quality and the shape of the book, make a negotiation with the seller and either store it locally or sent it to the nearest warehouse. All these, even with partnerships needs huge resources.
  • Ensuring the right mix of books in the inventory:- Unlike a marketplace based model, maintaining the right assortment of books is a big challenge. What if a lot of books are held up in inventory which has a meager demand?

B. Market Place-Based Model

In market place-based model, our platform would list sellers and connect it with buyers.

  1. The negotiations and deals are made by the sellers and the buyers among themselves. Our platform is just a facilitator.
  2. The buyer can buy a book from the platform; which the seller has listed. If the buyer and seller live at convenient locations for us, we would pick up the book from the seller and deliver it to the buyer.

Let’s evaluate the market place-based model:-


  1. Large pool and diverse availability of used books:- In the market place-based model, a large number of buyers and sellers can be connected together on one platform, thereby diversifying the used book assortment.
  2. Peer to peer selling within the same cluster:- Most used books buy and sale function is employed within the same cluster. Say, a college student in X semester can sell books to students in the X-1 semester and buy books from the X+1 semester kids. Similar is the condition with school kids or the parents who are trying to sell and buy used books for their kids.
  3. No inventory holding cost:- As margin in buying and selling used books is too little, any add on inventory holding cost is a setback.


  1. Too much of a work for the logistic partner:- When the buyer expects a home delivery, the logistics partner would go to the seller, evaluate the book, check it’s the condition. What if the book listed on the app is very different from what the seller is trying to dispose of? All of these and we are expecting from a logistics partner who isn’t much educated. A lot of resources has to be spent on training.
  2. Sellers negligence: What if the seller has sold the book yet not updated the listing on the app?

3. Analyzing Competitors

I have researched the top 5 apps (Olx, Bookscouter, Quickr, BookChor, Show My Book, Reuse Book) on the Google Play Store to buy and sell old books. I have gone through the reviews of the application on the Play Store, their core value proposition and design flow and will use the feedback while designing UX for the app.

What I am going with?

After evaluating both the models and considering the price sensitivity owing to inventory holding costs; and fluctuating demand of used books; I would go with a market place-based model of connecting the buyers and sellers of used books.

4. Designing The App

By going through the user reviews, personas, and affinity mapping, I assume the following are some of the pain points I can tackle in order to bring out the best end-to-end user experience while buying and selling used books.

Buyer’s Side:-

  • Able to buy used books easily.
  • Able to find photographs and all relevant details about the used books like condition, publisher, edition, etc before buying.
  • Able to get the book delivered to their footsteps.
  • Able to find the books well segregated and arranged by genre on the app.

Seller’s Side:-

  • Able to list the books hassle-free.
  • Able to negotiate with the buyer on his term.
  • Able to sell the books without moving out of his/her home.

Understanding Delivery Ecosystem

I have divided the delivery ecosystem into two cases. I’m not considering the logistics partner app here.

  1. Case 1:- First delves into the part where buyer and seller want to contact personally and make a deal among themselves.
  2. Case 2:- Second, is where they make a deal but a logistics partner picks up the used book from the seller and delivers it to the buyer. (I have made two assumptions here. A. This service is available in only selected cities. B. I am not considering the app of the logistic partner here.)

Let’s examine the user flow for buyers and sellers.

User Story For Buyer

As a buyer, I want to buy book one to one or get it delivered to me so that I have a convenient, fast and cheap way of buying used books.

User Flow For Buyer

User Flow For Buyer

User Story For Seller

As a seller, I want to sell book one to one or get it picked from my place so that I have a convenient, fast and cheap way of selling used books.

User Flow For Seller

User Flow for Seller

Wireframe (Buyer)

Step 1:- On-boarding to the app.

I have used Google Slides to make this wireframes. The app wants the location to suggest books near to the user. User is asked for his interest in the type of book he wants/possesses, to customize and personalize the home page.

Low Fidelity Wireframe of the on-boarding process

Good experience

  1. User can on-board to the app quickly and conveniently.
  2. User should see the home screen quickly and understand the core value proposition fast.

Bad experience

  1. Too many information like age, date of birth, photos being asked; in the onboarding process.

Step 2:- Home Screen

I have gone through the home screen of many online retailers apps like Myntra and Amazon as well as a few apps selling and buying used books. I narrowed down the objective of the user on the home screen to:-

  1. Visibility of the core feature:- Buy & Sell
  2. Able to find what he is looking for:- Search option
  3. Easily able to find the updates of his/her operations (i.e. buying and selling):- Notifications
  4. Able to find what more is there:- Menu option
  5. Able to see better content on the home page:- Recommendations and clear categorization

Home Page for the app user.

Step 3:- Buying Process

The buying process when a user selects a book ‘Biology 8th to buy’

  1. Screen 1:- A screen that appears when users taps ‘buy’ for the book on the home page.
  2. Screen 2:-The buyer enters his Pincode. pincode helps the buyer to identify whether doorstep delivery is applicable in his area or he needs to contact the seller directly.

Screen 2:-The buyer enters the price he is willing to make and requests the deal.

3. Screen 3:- The buyer enters how he wants to proceed with the deal — Buy Directly/Gets Book Delivered.

4. Screen 4: His request his pending for approval with the seller. Once the seller approves it, he gets a notification.

Buying Process

A: Screen when he wants to contact the seller directly.

B: When he wants door-step delivery.

A: Screen when he wants to contact the seller directly. B: When he wants door-step delivery.

Exploring the menu option:- What more is there?

I haven’t experimented a lot here but used the most common design patterns so that users can feel at home quickly.

Wireframes For Seller

Screen 1st:- My Book Listing Screen for the user.

Screen 2nd:- Seller enters Pincode.

Note:- Here, the pickup facility isn’t available for the seller. If it was, the next flow would ask for his preferences. I haven’t shown it here.

Seller entering details about the used books.

My Buyings

This is where a buyer will see all his buyings.

  1. The buying type:- Direct Buying and Ordered is separated.
  2. Filter option:- To filter the buying — By Type and By Deal Status


To be true, it was a long exercise but each step of the journey from the last 4 days have been amazing. I have a skipped a few wireframes (which I thought were self-explanatory) due to paucity of time. Thanks, for going through this exercise extensively and coming to the end. I’m waiting to hear from you. Suggestions/Criticism/Applauses (:p)! Tada!

Quick Design

Find top tutorials & courses to learn UI, UX, wireframing, design, graphic design, mobile design, web design, product Design, logo design, design thinking, design tools, Sketch, Figma, Photoshop, Illustrator, Flinto, After Effects, Axure RP, InDesign, Farmer JS, 3D design & more

Venkatesh Gupta

Written by

Product @ Internshala | Passionate about start-ups, ed-techs, yoga, folk music, travel, writing or anything that’s not cliche? Let’s e-meet

Quick Design

Find top tutorials & courses to learn UI, UX, wireframing, design, graphic design, mobile design, web design, product Design, logo design, design thinking, design tools, Sketch, Figma, Photoshop, Illustrator, Flinto, After Effects, Axure RP, InDesign, Farmer JS, 3D design & more

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