Pretty much anything you need to know about Debian is available at
Debian -- Documentation most of which you can install on your system and browse at your leisure.
Another online resource is
Debian GNU/Linux Desktop Survival Guide unfortunately the "small" fee the author wants for a pdf version is $30. Not what I would consider a small fee.
Learning Debian GNU/Linux
is also available to read online.
Here is a good site with quite a few Linux books online
Free Linux Books .
Why pay money when most of the resources you will ever need are available online.
Not quite Debian, but Knoppix is based on Debian and there is a lot of good info here
Knowing Knoppix
Plus there is documentation for most programs in /usr/share/doc at least that's where it is on my system.
Amazon has quite quite a few books on Debian. "Results for: Debian Linux"
http://www.amazon.com/exec/obidos/ex...Mozilla-search
Debian is great..