This section lists a few good books in several areas.
Harley Hahn's Student Guide to UNIX, second edition; McGraw-Hill; ISBN 0-07-025492-3; 1996. Not just for students, this is a complete and very readable guide to UNIX and networking.
UNIX for the Impatient by Paul W. Abrahams and Bruce Larson; Addison-Wesley; 1996. Terse and detailed, for people comfortable with technical material.
UNIX Power Tools, second edition, by Jerry Peek, Tim O'Reilly, Mike Loukides, and others; O'Reilly & Associates; ISBN 1-56592-260-3; 1997. A huge collection of tips, techniques, and concepts for making intermediate users into advanced users.
UNIX in a Nutshell: System V Edition by Daniel Gilly and the staff of O'Reilly & Associates; ISBN 1-56592-001-5; 1992. From user commands to programmers' utilities, this book covers UNIX with concise descriptions and illustrative examples.
Linux in a Nutshell by Jessica Perry Hekman and the staff of O'Reilly & Associates; ISBN 1-56592-167-4; 1997. A complete reference for Linux.