Listed below are my recommended reads on Linux and UNIX.

Learning Red Hat Linux (O'Reilly)

If you are new to Linux, you should definitely consider getting this book. It's a quick and useful read with helpful information for installing Linux. It also comes with the Red Hat 7.2 CDs.

Linux System Administration (Prentice Hall PTR)

There isn't a single GUI in the entire book (good or bad depending on your perspective). It does an excellent job describing how to configure your system and goes into the contents of config files in detail. Not for the faint of heart. The authors have a good sense of humor to boot.

UNIX Shell Programming (Hayden)

The old-school classic. There is no better book that covers shell scripting.

The Cathedral & the Bazaar (O'Reilly)

Fascinating read on the open source phenomenon. Good insight on why open source development has been so successful. The essays from the book are available online.

Linux in a Nutshell (O'Reilly)

A useful reference. Covers not only UNIX commands, but editors, version control (CVS), etc. Not helpful for administration or installing Linux (see previous 2 books).