I needed a book that would teach me REGEX and how better to use grep/fgrep, but without having to learn PERL and JAVA. (ie. Master Regular Expressions contains over half the data relevant to other languages.)
This "grep Pocket Reference" did a good job of explaining the grep options in tandem with the it's Manual Page. Although few, I thought the examples near the end were great. However, the examples seemed to be themed on personal private data searching rather then something more relevant to a computer users -- but they could easily be converted.
This EBook needs some corrections (a reprint including errata?) as it contains some grammar or run-on sentences which conflict and provide incorrect data. Also, there's a sentence in the book stating, in effect, it's OK or legal to use fgrep to search other peoples EMail. I'm no lawyer, but this doesn't sound correct. Again, those few sentences probably need a little rewording.
All in all, besides the fact it needed a good proof reading -- the book taught me what I needed to learn about grep as it's manual page lacks examples and a certain amount of clarity. (Currently, grep's manual page is written like a specification rather then something focused towards a user, omitting example usage.)
(There is a small chapter on Perl REGEX. ie. --perl-regexp)
If you need a book to learn REGEX and have a little trouble with the GREP Manual Page, or don't want to read a huge book like Mastering REGEX, get this book for learning REGEX (aka BRE/ERE).
Also noteworthy, the MOBI formated EBook version of this "grep Pocket Reference" is the first readable MOBI EBook I've been able to read so far on my Kindle DXG. This book had few TABLE TAGS (or computer technical drawings/coding). And of the presented console/terminal text presented, it was readable unlike many other MOBI technical books I've tried to read.
Edited 2011.11.19: Also, GREP originates from the line editor called 'ed' (ie. command syntax: g/re/p) according to the author Robbins of the book sed & awk (2nd Edition). The third chapter of the sed & awk (2nd Edition) is devoted to regular expressions (grep), as sed & awk depend on this feature for searching.