This book had some definite strengths, but I'm sorry to say that I thought the weaknesses outweighed them. I'll begin with those weaknesses so that I can end on a more positive note with the strengths.
First of all (and I know this is cosmetic, but I feel it can make a big difference in enjoyment of a read), the amount of typos was appalling. Two or even three I can accept in these days of editor cut-backs in the publishing industry, but "their" instead of "there", extra or missing "a"s and "an"s, periods where there should be commas, "to" instead of "do"... the list went on and on.
If a book is otherwise strong, I can grit my teeth and forge ahead, but the second problem was deeper. I believe that this second problem was actually related to the author's strength: He knows his material too well. He had done so much research and spent so much time interviewing boat crews that I can only imagine how fresh and clear it all must have seemed to him while writing. Unfortunately, he was not able to transfer his knowledge clearly to the reader. The book contained a huge amount of acronyms and slang (many period), sometimes explained once, sometimes never, but filling every page. If you aren't familiar with submarines, or navy structure, these quickly became confusing. Add to this the author's penchant to switch between first names, last names, ranks, and nicknames, and it was very difficult to keep the many men involved clear.
Continuing on this confusion, the book was not clearly organized. Although I could see from the chapter titles how he was attempting to organize the information, it lacked coherence. The overall narrative jumped from one point in time to another (and not in a clear switch between a main narrative and side-stories, but all over), and then shorter anecdotes would be embedded in these without any warning.
I spent a frustrating amount of time online doing my own research to clarify things. It took 100 pages before the author even clearly stated what "pack tactics" were, although the narrative of the first two chapters assumed that you knew.
All of that said, the book has heart. The subject matter was clearly important to the author, and all of those (often frustrating) anecdotes and side-stories helped to humanize the "characters" in the submarines, command headquarters, and research labs. From the stories of the submarine patrols, I incidentally got a much better feel for the time scales involved in their maneuvers, both attack and evasive. Amazing.
The author's research is (in most cases) meticulously documented, and the actual pieces he included from letters, orders, and other documents were great. There is an extensive index as well, although it is mainly composed of names. The period photos are great. If I could wish for anything, though, it would have been a section on the acronyms, and perhaps a diagram of the fleet submarine so that I could better visualize rooms and equipment mentioned in the narrative.