Recently bought "Regular Expressions Cookbook 2nd ed." and wanted to share my findings.
The second part of the book (6 chapters) is the cookbook part. Every chapter shows several commonly used problems/solutions. The chapters are "Validation and Formatting", "Words, Lines and Special Characters", "Numbers", "Source Code and Log Files", "URLs and Paths" and "Markup and Data Formats". In all it shows how to use 140 regexes.
Each chapter tackles one specific task, for example "Validate Credit Card Number". The chapter starts with the problem description, followed by the solution. The solution can be extensive, depending on whether flavour specific constructs are used in that instance. After that is a discussion part, describing more about the issue, making everything clear. Sometimes a variations part is added, to show you how to add additional information to the initial problem. Finally, a see also section points you to similar/relative solutions in the book.
All in all I think this second edition is an excellent regex book. Do not buy this thinking you will get a comprehensive beginner's guide to regexes in a single language. In my opinion some basic knowledge is required, unless you are looking for the ready made solutions. The best part of this book, for me personally, is the side-by-side comparison of the different flavours. I am quite sure that this book will stay on my desk, as a good reference on how to get things done.
If you want to see more information, visit O'Reilly. If you decide to buy, make sure you have the right version (August 2012).