The Horse Book.
The quintessential reference for the Linux Operating System. Not exactly the kind of book you want ot curl up with in from of a fireplace, but if you can't figure out how to use "chmod" or figure out why man pages keep popping up when you press 'K', it's quite irreplaceable. Probably into it's third or fourth revisions by now; my copy, however, is slighly old. Here are the details as they pertain to my said copy:
Name: Linux in a Nutshell - A Desktop Quick Reference
Author: Jessica Perry Hekman
Date Published: 1997
Publisher: O'Reily and Associates
List Price: 19.99 USD / 28.95 CAD