The first chapter covers CodeIgniter's MVC framework, which provides a way for a programmer to logically partition code so it's easier to maintain. For those of us who aren't accomplished PHP coders, this chapter also contains a PHP style guide, which I thought was a nice feature. By the way, the code snippets throughout the book are clean and easy to read-- the author must have followed his own advice on code style.
The second chapter is an introduction to some of the more productive libraries you'll find in CodeIgniter. Here you'll find some excellent advice on how to take timing metrics in your application, how to secure it, and how to accomplish routine activities like retreiving data from the user's request. Other 'web topics' are addressed here, like how to manipulate the session, how to manage emails and file uploads, and much more.
Chapter 3 handles form inputs and databases. As is common throughout the book, the reader is given minimal technical overview. What you'll find instead is a very brief explanation of what's about to be covered, then a few very readable source lines that demonstrate use of CodeIgniter in action. If this book were your only resource, I'm sure there would be times where you didn't find enough material to get everything done you wanted to do. But if you have a web browser (and Google) handy, a book of this type can be an effective index to help you find the parts of a framework you want to leverage.
The next few chapters cover user authentication and application security. I found these to be a little spotty-- heavy in some places, light in others. Still, the material was useful and not difficult to read or understand.
A nice chapter on tips for building a large-scale application was next. I found this one interesting-- many of the ideas were well-known, but a few had not occurred to me before. I liked reading it. Next up was a chapter on Web Services. I didn't take the time to test the provided code for this chapter, but I would like to sometime. If it works as I hope it will, I may have a new way to stand-up test web services!
The final 2 chapters are on extending CodeIgniter (it's great that the library authors institutionalized this!) and donating code back to the community.
So who is this book for? The book itself tells you it's for expert PHP coders, but I don't believe that's exactly right. Given the easy-to-read nature of the book and the light treatment given to some of the meatier topics, I'd say this book is about right for a novice-to-intermediate level PHP coder. I haven't done a lot in PHP, yet I found the code reading very easy.
If I had a wish for the book, I'd wish for a little more depth in the harder topics and maybe some quick overviews for a few topics. (Diagrams accompanying the overviews would be nice, too. This book has few illustrations except for screen-shots.)
All things considered, I'd recommend this book to coders that are getting started with PHP and CodeIgniter. It's easy to read and will get the reader pointed in the right direction for solving many web problems.
The book (and a sample chapter) can be found here: https://www.packtpub.com/codeigniter-1-7-professional-development/book