I don't use an e-reader, but I found a long time ago I prefer audio books to physical books.

Its purely a comfort thing. I can read a lot faster than any audio book, but I just have a hard time finding a comfortable position to read a real book.

Also the added benifit of listening in the car, while working, or falling alseep.

The only times I find myself with a physical book is reading technical things like textbooks, or when I'm on a plane.