This is a very comprehensive work! The author is not only meticulous in describing practically each u-boat sailing during this period, but he tends to keep the reader's interest in what could be a dull assignment, by explaining pertinent background information and providing in-depth detail on various crew members, making many of them "come to life" in the words on the page. At the same time, he keeps the reader informed on what is going on in other parts of the war that could affect u-boat and ASW (anti-submarine warfare) operations and practices, such as code breaking, Hitler's rash decision-making, Operation Torch, dropping off of secret agents, sabateurs, and/or commandos into enemy territory, development of radar and sonar and HF direction finding, u-boat activity on the U.S. coast, military officials involved, etc. This book is important historically since it not only provides an extremely detailed account of operations, but it reviews it from an American standpoint based on the author's incredible current research and his reading of British historians, and then commenting on divergences of viewpoint or, in some cases, the lack of British commentary on certain embarrassing happenings. - As some reviewers have noted, Blair tends to "stick with the facts" instead of sensationalising, and in the process gains the reader's trust. Excellent u-boat history, engrossing reading.