I dunno, I've always considered Advanced Bash Scripting to be pretty poor for the beginner. It starts with various scripts, little or no explanation of why, basically, similar to far too much Linux documentation. It's always difficult to find the proper balance between how and why, especially as some people do better at understanding the how after learning the why and others understand the why, once they learn the how.
Everyone learns in different ways, and the others who have posted here disagree.
Obviously, you have to decide for yourself what you find useful.
The Advanced guide can be useful, but I fear that I don't share others' high opinion of it.
The Rute book, listed above, is, IMHO, excellent.
I also like
http://steve-parker.org/sh/sh.shtml
I have my own little page of links that *I* found useful when first trying to figure it out. For what it's worth...
http://home.roadrunner.com/~computer...scripting.html