In a new post to his blog today Chris Hartjes has a book review of the Packt Publishing book "CodeIgniter 1.7: Professional Development".
When I read a book about a programming framework, I’m expecting to see that they start off with the basics of using the framework, then keep expanding on the abilities of the framework. By the end of the book, you should be able to build something OTHER than the example application (if they provide one). [...] This book starts with the basics of the framework, and patiently builds on the concepts you previously learned. Good, clear examples of how to do things.
He mentions two of the interesting things the book touches on that some introductory books tend to leave out - coverage of extending the framework itself and how to worry about scalability. Overall he recommends the book to anyone looking to do CodeIgniter development.