I started reading more pre-1900 books that I wouldn't want to carry around with me.  I like that I can now carry a tome (several in fact) in a 9 oz. format.
It has got me to read more in the last couple of years since I got it.  I am averaging 35-40 books a year since I bought my reader. 
Back in the paperback days, I hated to get something too thick as I don't like to stress the spine of the book to breaking it.  I treat my books with great care and always felt bad if I did break the spine.  Now I don't have to worry about it in the world of e-books.  
 
-Seth Williams,
San Francisco, CA