Security
Hacking Exposed (any of the series)
Incident Response: Ivestigating computer crime
"safe book" Pratical UNIX and Internet security O'rielly
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Programming
Any of the Sam's Teach Yourself Series
UNIX Network Programming volume I
Advanced Programming in the UNIX Environment
Linux Socket Programming by Example
"the Camel book" O'reilly perl book
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Networking
Computer Networks
TCP/IP Illustrated volumes I & II
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

"Snail book" O'rielly SSH

Any books by Peltier, Thomas R.
http://www.amazon.com/exec/obidos/se...115660-6043359



Some of these are considered to be the "bibles of the trade"