Project Gutenberg, if you don't know, is a webpage collecting electronic books online. It was founded in 1971 (yes, long before the Internet as we know it today existed), when Hart typed the Declaration of Independency on a Xerox mainframe. Hart can be seen as the inventor of electronic books - 40 years ago.
We're still waiting for ebooks to get into mainstream. Currently, ebook reading devices are available, but their usage is not widespread yet. But I'm almost certain that ebooks will become very important within the next years. Hart had that opinion 40 years ago.
Today, Project Gutenberg has about 36.000 books. Most of them are public domain, because their copyright expired. There are other similar projects today: Wikisource is a sister project of Wikipedia and archive.org has a lot of scanned books, including most of the public domain books digitalized by Google.
Some mission statements for Project Gutenberg from Michael S. Hart (taken from Wikipedia) I find that sum up things very well:
"Encourage the Creation and Distribution of eBooks"
"Help Break Down the Bars of Ignorance and Illiteracy"
"Give As Many eBooks to As Many People As Possible"