the best way to learn about various commands is once you read the man pages, if you are still struggleing look up the command online or in google groups and you will usually see a example of how other people use it. thus explanine how and what it does due to context.
as far as scripting books, i havent seen a book on unix scripting, but there are plenty of books on unix shells. IE "Learing the Korn Shell" when reading this book they explane alot of the scripting you can do w/ korn. well at least the logic portions. learning differnt commands is a job most people leave to the man pages.
but if you seriously want to get into unix scripting/programming skip the shell programming and go stright to perl. it can do ALOT and it can do very little. it is an extreamly easy language to learn (IMHO) and the books by oreilly are well... oreilly has made there books absoultly easy to read and even easier to follow (most of the ones i have read anyways).
Start with:
Learning Perl
Mastering Regular Expressions
Learning Perl Objects, references & modules
Programming Perl (use as a referance)
Perl Cookbook (use as a referance)
the first 3 books will get you codeing perl scipts/programs so fast its reduclious and you will feel alot more confident.
the userbase for perl is HUGE. for a user group in your area check out
www.pm.org.