Firstly, this book describes quite well English people and It can help us to understand them, but I think that it’s also exaggerated and it generalizes too much.
Secondly this book mentions a lot of strange behaviours but it doesn’t mention others that a foreigner has to know: For example British drive their cars on the left of the road, they use different money (pounds) or different units of size and weight. This book offers you some rules about not feeling an alien in England. They will help you to be more like the English.
On the whole, this book can help you if you travel to the United Kingdom.