Well written, and politely explains and acknowledges his sources as he proceeds. Moreover at least he works towards a conclusion and so keeps the reader's attention. (Author was a former suspense writer). It recaptures some of the strange atmosphere of 1940-41, if only with the photos.
Its claims are, however, historically worthless. By all means get the book, but only if you want fiction--in fact the author should have written it as that. Hayward and Foynes (quoted in the text, I think), who did the real research, would not endorse it! Nor would the Germans, who have now put their E-Boat and similar histories into print and online.