The Guttenburg Project (ebooks)
You and your kids can read to your hearts content with http://www.gutenberg.org/ . With over 18,000 free books in the Project Gutenberg Online Book Catalog. There is no way you could read all of these books in a lifetime. In the United States, all of these books are in the Public Domain, so you can also print and distribute them if you wish. They include all of the classics like Mark Twain, Shakespeare, The Wizard of Oz. The pictures and illustrations are public domain too!