The most positive characteristic of this book is its accessibility: it's the only PHP book that I have read without frequently thinking "what on earth do they mean by that?" The writing style is not formal - in fact, it's too flippant on occasions - but it's well written and easy to follow. It succeeded in getting me to understand one or two functions that had previously been confusing and the introduction to regular expressions would make a good grounding before tackling more advanced regex tasks. I really liked the "What can go wrong" segments: every programming book should have such information separated out like that.
The structure is slightly less well-ordered, though: it has a habit of referring to previous or forthcoming information, so you will be flicking back and forth at times. The incomplete code archive was a big annoyance: you will face some careful typing when you want to try out the examples for yourself. This is a second edition, so the archive should have been sorted by now.
I was disappointed with its incomplete treatment of most of its topics; more than is usual for this type of book. I was really interested in the details of processing form content into e-mails, but this important core function of any website gets little more than brief coverage of validation. The first chapter is titled "The Scripts That Every PHP Programmer Wants to Know", but it missed a lot that could and should have been included. Maybe it was a bit too ambitious in its aims for a book of this modest size, and it left me with a lot of unanswered questions. Although, I must point out that the other books in my possession didn't answer them very well either. I would also like to have seen an explanation of the use of single and double quotes, which I wanted to know: the authors have used both types but never clarified why.
Aside from my caveats, the good points are just about enough for me to recommend this book as an addition to a collection of PHP books. As a supplement to other books, it did give me a few useful snippets that I had not seen elsewhere. Just don't pick this up as your first PHP book or expect it to solve all of the scripting problems that you might expect it to.