Despite only awarding this book three stars, it is well worth the price in terms of usefulness, being for the moment at least, something of a niche product.
There is no 'who is this book for' or 'how to read this book' section, by page 5 the snippets appear.
The book has the same struture as osCommerce with an install, admin and catalog section.
This book is quite small and there are a lot of long code snippets which dont really lead to more than a brief discussion. Almost a page of setting constants leads to a brief discussion of the benefits of defining them. There are also a lot of screen shots, the use of which is justified, however, its left me wondering what would be left in terms of content if all code and shots were stripped out.
'The nuts and bolts of oscommerce customisation' is a fair description, but 'the programmers guide is not'. I would describe this as a code review. That said, there are plenty of PHP books out there already.
All in all, I am a happy customer, oscommerce books are thin on the ground, Im glad the authors took the time to write this book and for the price its well worth having.