There are a number of efforts underway to bring the full content of copyrighted and out-of-copyright books to the web. Here are several notable efforts worth looking at.
Early English Books Online - More than 25,000 manually transcribed texts from the first 200 years of the printed book (1473-1700), with an additional 40,000 texts are planned for release into the public domain by the end of the decade.
Forgotten Books - mostly 19th and early 20th century works, and thus quite useful for historical context.
HathiTrust Digital Library - Partnership designed to preserve and provide access to digitized book and journal content from partner library collections.