This book is a list of about 250 monsters, mostly from Fighting Fantasy gamebooks, and are intended to be a support for Directors of Advanced Fighting Fantasy roleplay games.
There are good images (mostly taken from other publications of Fighting Fantasy series), stat bloks, descriptions with a bit of background that usually goes beyond the short descriptions in the gamebooks, adding flavour and insight.
All in all it is useful and interesting, if you Direct an Advanced Fighting Fantasy game. I'd say you really NEED to have this book, if you are a Director.
This book can be used both with "first edition" Advanced Fighting Fantasy RPG and with second edition. If you are using second edition rules (by far the most commonly used), in the main Advanced Fighting Fantasy rulebook, at page 123 and following, you can find a quick list of the few stats and detail (armour, weapon, special features) that have been added with the second edition and that are required to fill the gaps of this book.
This same book, originally printed in the late Eighties, has been recently reprinted by Arion games with a different format (bigger pages and smaller fonts), but the contents are EXACTLY the same as the Eighties edition. This means that, if you want to save a buck, you can buy a second end edition from the Eighties (that costs next to nothing + transport) and you still have the same information and value for Directing your gaming sessions, but you save enough money to buy a pizza to be eaten while you play, on top of it.