If you're looking for a handy desktop reference this book is NOT it. When faced with a short-fused development schedule and needing to get up to speed with regexps rather quickly I found the book to be difficult to navigate, inconcise, and the overuse of bold, italics, and foreign (Japanese?) characters and other oddities very annoying. I thought the book went way beyond regular expressions and therefore found it of little use as a reference guide. It is better suited as a tutorial for someone that has a lot of time on his/her hands. A much better reference, also from O'Reilly, can be found in "JavaScript - The Definitive Reference", by Danny Goodman.