This is a rework of the original book by the original author. Supposedly it contains more unclassified information than the previous edition due to the passage of time. Maybe it does, but if so that is not clearly shown, nor is there any more clarity as to the cause of the sinking than before. In one brief paragraph a sudden conclusion that does differ from the past is raised, but not supported by any evidence or explantion. It appears as one paragraph at the end of a chapter!