If you are looking for a quick tour on how to develop a Joomla 1.5 Extension, then this is a good starting point. Unfortunately this lightweight book is very sketchy and suffers from problems. Firstly, there are bugs in the code - by no means difficult to fix for a PHP coder of experience, but it is an annoyance nevertheless. Secondly, there are omissions in the code - some functionality has been missed out of the walk-through example in the book. Thirdly, important topics are not discussed at all, such as client side and server side validation.