I brought this book to prepare myself for flat-hunting, however having shared before I found most of the points it mentioned where either common sense or basic knowledge.
The book is a great introduction to flatsharing and gives some nice tips and pointers as well as case studies. However it often mention things without going into enough detail about them(ie contracts), for people who have shared before you're probably not going to learn much.
Summary: Great introductory book if you've never shared before or even if you're looking for a few pointers. However doesn't really go into enough depth to really be useful.
Note: The booked is based on England and does mention in places where this would make a difference. The book also has a strong focus on finding flats via the web (in particular the authors own flatshare website which actually has good, if not better in some cases, advice for free on it)