In this book Alastair Mars summarises British submarine operations in WW2. All significant actions get a mention. The book provides an interesting overview of the British submarine force during the war. Mars was himself a participant in some of those actions and he has added his own opinions to the text in several places. I find these interesting. It's not a bad book, but only someone interested in the subject will want to read it, and to such a person it will reveal nothing new.