The Wikipedia has an extensive article on e-books, structured and being filled in by enthusiastic volunteers. It's the first place to go.

For our thoughts on e-books, follow this link to our ebook info pages. You can go directly to an essay on formats, a group of essays on e-book futures/the future of e-books, or a discussion of the buyer's rights regarding the e-book she has just bought.

One recent update: Cory Doctorow, author and tech guru, has written some interesting things about the current state of e-books, publishing, and copyright. If you look around his site you can also find his recent novels available for free download.