I just thought I'd mention this for any non-fiction e-book fans wandering through:
The National Academies Press offers literally hundreds of free PDF versions of their publications. I think it's mostly the bestsellers that they charge for the PDFs, but even then they usually let you read the book online (html frame) for free.
I generally hang out in the Conflict and Security section, but they have the whole spectrum of sociology, science and technology too. If you're a student, it's a great research resource, and if you just like to keep learning, they have so many topics of interest, your head will explode :)