Note: this is a Flash 5 book. It contains no Flash MX content. There are significant changes to Flash in the MX version that make some of this book outdated.
This book would be ideal for someone who already knows a bit about each topic: actionscript, php, sql, but hasn't built anything with those languages yet. Maybe a Flash coder who's worked with a server-side programmer on a project, and now has to work alone?
It's decently written, with an occasional sense of humor. The writing is terse, and you won't get more than one explanation of each concept. The information comes thick and fast, with discussions of server protocols, mySQL, and PHP diving right in. Basic introductory material is brief or non-existant. In fact, if you don't already know something about PHP, you couldn't get any of this stuff to work, as you'll have to know how and where to put it on the server.
One very big problem is that there's almost no distinction between "code we're showing you to illustrate a concept" and "code that's part of the application we're building." The authors will often just toss a couple of lines of code into a page, and it turns out to be something that needs to get added deep within a script you've been writing. Miss that line and everything will break.
The Flash code is good, although I wondered why the authors occassionaly used the ancient setProperty syntax and "eq" operators from Flash 4.
You can get this book easily for about a third of the list price, and for that it's certainly worth it, if for nothing but a good introduction to the concepts here.