Especially now with their holiday sale, you'll find a lot of variety at pretty spectacular prices, and since everything is downloadable it can be bought and gifted without ever leaving the house.

I still find Amazon to be pretty great for books and most other things, so I see nothing wrong with going that direction either. A giftcard, or even a package of books (amazon offers some gift wrapping services for a small additional fee) would make a good gift, imo.