Rating: 

I recommend getting this book

if you feel comfortable with regular expressions

and regular expressions are important to you.

As one expects from an O'Reilly Pocket Reference,

this book is compact but still covers a lot of ground.

For a whole bunch of applications, it provides:

tables of various groupings of regex metacharacters'

summarizing their syntax and meaning,

summaries of other regex related features

but not in tabular form,

examples,

and a few references in case you need to go deeper.

The information is concise and well chosen.

This is a reference,

but in applications where you use regular expressions less,

it may also be useful for expanding your knowledge significantly.

It was for me.

If you wish, take a look at my

more detailed review.