I like this app idea I thought of something similar myself a while ago. In my case though I focus primarily on building it on top of Amazon.
One because of all the books you can buy on there.
Two, I’m 13 year plus Audible.com member and probably have 450 books on the platform if not more. This feels like something GoodReads should have become but it seems since they sold to Amazon it’s dying a slow death.