If like me (and most people) you learn best from examples, this is just the book to read to find out how to write shell scripts. Actually it is a petty good book to look at if you just want to learn how to be a more effective user of any flavour of Unix: Linux, Ubuntu, Solaris, Red-hat, etc, etc. Obviously, you do have to be a Unix user for this stuff to be useful.
Material is presented in a logical order; it has lots of examples, and the explanations are clear. It begins with very simple things, and ends up with very powerful scripts particularly useful to system administrators.