Tools and Techniques for Computer Typesetting Ser.: LaTeX Companion by Frank Mittelbach, David Carlisle, Michel Goossens and Johannes Braams (2004, CD-ROM / Trade Paperback)
The single best guide to LaTeX available in the printed press. Although there is plenty of blogs and guidance on how to solve problems in LaTeX, this book provides the convenience and the easiness of use that only a book can give. I strongly recommend it to anybody willing to get some structured assistance when working with laTeX.