Can you borrow a book and return it when you finish it?

No it's a book store to buy book

Agreed, they aren't meant to be a library. They have chairs to read in so you can get a feel for the book, but purchases aren't meant to be temporary.

I don't think so. I've never heard of them doing that. You're welcome to sit there and read it, then return it to the shelf afterwards without leaving the store.