At LifeHacker I found the following post:
Tech-book aggregator eBookSpyder has the complete text of the Ubuntu Linux Bible available for download as a PDF.
As you might expect from the title, the 931-page book covers everything you need to know about installing, configuring and using Ubuntu. It teaches you groups, graphics, gaming, spreadsheets, e-mail and much more. It's an impressively comprehensive guide--highly recommended for anyone interested in Ubuntu. Indeed, if you find the e-book useful, why not support the author and buy the hardcopy version? Either way, you'll need a password to unlock the PDF: It's 'ebookspyder.net' (without the apostrophes, of course). — Rick Broida
Ubuntu Linux Bible [eBookSpyder]
Learn Ubuntu Linux with freely available e-book - Lifehacker