I recently purchased this book, and as some of the other reviewers have said, it rarely leaves my desk. I found this book to be written at an ideal level of difficulty for someone with a good working knowledge of HTML, and NOTHING more.
This book has helped me develop from a static HTML designer to a capable PHP programmer. The book covers a number of topics that I'd always wanted to use on my sites, including: cookies, sessions, interactive forms, and database connectivity, including an introduction to using SQL to connect to a number of different databases.
The book has a number of tutorials and examples which perform the key function of transferring what you are learning into practical examples (often lacking in beginning books).
There is also a great appendix of functions that gives the new programmer a reference to which they can refer for quick answers. Finally, and maybe best of all, Wrox has a great Web site with a number of forums related to the topics covered in the book.
Overall, it's a great book for beginners. I used what I'd learned in the first week to add a number of dynamic features to my own Web sites, and the difference was instantly noticeable. Best of luck!