Mastering Regular Expressions

I read the first edition many years ago and while I don't remember the contents in detail, I get the impression that this edition has a much smoother opening than its predecessor, and is thus an easier book to read for less experienced programmers. The first few chapters teach the core techniques, with could recaps and summaries, as well as a lot of useful examples.

The second half of the book is much more advanced and focuses more on the technical aspects of regex engines, ways of maximizing efficiency in regular expressions and chapters on the implementation of regular expressions in various programming languages, including Perl, Java, and PHP.

It is really a classic work and a must for anyone who wants to learn how to think about regular expressions instead of just viewing a list of metacharacters found in a language documentation file.