If you think that all caterpillars look the same, then this authoritative and academic work will disabuse you in most respects. There is a bewildering array of variations on the theme caterpillar, and this book displays photographs of virtually all UK species.
The standard of photography is very high, as are the production values of the book. It is clear that Mr Porter knows his stuff and you will find no better guide to our caterpillars than this. However, as anyone with an interest in birds will know, photographic guides have their flaws. In particular, they show individual caterpillars at a chosen moment in time, rather than all the important features that a good artist would be able to capture. Lighting and backgrounds in this book are generally good, but they do have an influence.
The biggest flaw in this book is that all the caterpillars are shown to be the same size. Fine from a design point of view, but not always helpful, especially for species whose appearance changes as they grow.
In short, this is a good companion volume to Skinner's Moths Guide, but suffers from similar shortcomings. They both feel like the works of avid enthusiasts for their subject, but I wish that someone with a similar enthusiasm for their readers' needs had been able to to take the production in hand.