First, you’ll need MS Reader
Essentially, ebooks work like this… As long as the book you’re looking for exists in the open domain, you should be able to find it. If you’re trying to read Leonardo Da Vinci, it will be free, if you want to read The Davinci Code, you’ll have to pay for it.
Now, browse to your heart’s content:
Amazon.com Ebook section… mostly pay books
Baltimore Public Library http://www.bcplonline.org/centers/library/wob_ebooks.html
Internet Public Library http://www.ipl.org/
University of Virginia. Excellent Resource http://etext.lib.virginia.edu/ebooks/