The Internet Archive is a non-profit digital library with the stated mission of "universal access to all knowledge". The Internet Archive permanent handles the storage of and free public access to collections of digitized materials, including websites, music, moving images, and nearly 3 million public-domain books. The only problem is that it costs so much to share that infomation with direct downloads, torrents are the perfect way to share this legal content.
Torrent is a protocol for computers to communicate and share files in such a way that as a user downloads a file they share it as well. When a user has the full download they can choose to seed the torrent longer or remove it from the torrent application while keeping the downloaded data. A single torrent file can have hundreds of files in it, and users can choose to download certain files or the whole torrent.
A torrent file only works with a torrent downloading program. The Opera web browser can handle torrent files and I'd recommend using Opera, it has allot of good features and is secure. If your running a Linux operating system there is most likely a torrent application installed by default. For windows users the best torrent programs are Azureus which is open source and hosted by sourceforge.net it is also a torrent browser and media player. Utorrent also has torrent browsing capabilities but is more lightweight.
Internet Archive blog post - 1000000-torrents-of-downloadable-books-music-and-movies
Internet Archive - Torrent Hotlist
Internet Archive - Torrents Over a Million Books