The biggest problem I have with most stores is the way they show and filter their books.
I can never find a book I may like unless I know the author or title.
I want to be able to search by category
I want to be able to see the cover, but I also want to be able to turn off the cover (so more books fit on a page)
I want to be able to read a short part of the book
I want to be able to manage my library within the shop
Nice to haves are:
Books I might like, based on books I have bought (not based on books I have looked at!)