There is a lot of good documentation included with linux. Even the info manuals look good if you install from source, and use "make pdf" or "make ps" or "make dvi".
For example, the manual for bash is called bashref. It is about 150 pages long. If your system is rpm based, you could install the source rpm. Then in the /usr/src/packages/SPECS directory execute as root "rpmbuild -bp" to apply the patches. Next cd to the the bash source in the build directory:
./configure && make pdf
The PDFs will be in the doc/ subdirectory.
Packages to consider doing this for are:
coreutils, bash, find and tar.
Also search through the descriptions of packages that contain "doc" in them.
SuSE linux and other distro's have included a package containing all of the howto's from the Linux Documentation Project web site. www.tldp.org
Going to the www.tldp.org
website anyway would be a good idea. There is a link to a Linux-Gazette site where you can download all of their archived magazines. They are in html form.
If you install "swat", web based Samba configuration, the initial page at www.localhost:901
contains links to web-based man pages and howto's, including some web-books:
Using Samba, 2ed. - by Jay Ts, Robert Eckstein, and David Collier-Brown
The Official Samba HOWTO and Reference Guide
Samba 3 by Example
The Samba Developer Guide
The same is true of the cups web interface at localhost:631
Good Luck hunting for the best documentation on the way to becoming a Linux Guru.