I have known that I am a coeliac for two years (after a lifetime of symptoms!). I have bought most (I think) of the other books on the market, many of which have an intro on coeliac then mostly recipes and coping strategies. They are all good.
This is better - at the explanation part especially. Prof Peter Howdle is head of the Academic Medical Unit and Consultant Gastroenterologist at St.James's University Hosp. Leeds. As such his explations are detailed and thorough, easy to read, with good diagrammes and notes. The first part of the book is the science, then the caring and coping. Particularly good are the 'patient question and answer' inserts. It also contains an excellent glossary and useful addresses of organisations and suppliers and gluten-free cookery books.
This book is endorsed by Coeliac UK - (SUPERB - JOIN!!) and really does appear to be the definitive guide.
My only reservation would be that if you were newly diagnosed and trying to come to terms with the condition, causes and limitations, you could find the science a little overwhelming until it all sinks in.
For the ultimate explanation, this is highly recommended.