I think of typography as the design of letters—the shapes, strokes, and weights of individual letters. Typography is incredibly fascinating to me, but I admit I’m not an expert in it. Fortunately, there are a lot of great articles on Medium about typography. Here’s a nice collection of typography books and resources if you’re interested: https://medium.com/@crazydelic/typography-resources-find-good-fonts-1a2c5f27933e#.ll6rr5z46
As for the design of words, I honestly haven’t found many books on it. The one book that had a big influence on my writing is Don’t Make Me Think by Steve Krug. It’s not specifically about writing, but it’s one of my favorite books about usability.