The army list is good with a good selection of troops.

The background is good also giving you a history of this opportunist race. Somthing which is now lacking in the new army books from warhammer.

The special character are interesting and diffrent from each other and have a detailed background.

The tactics given are also useful and have some nasty tricks to use on your opponents.

This book is now obsolete and the new skaven book will be out early next year, but if you want a more detailed background I recommend this book.