BLACK MAY, by Michael Gannon, HarperCollins, 492 pages, $30.

May 1943 was the deadliest month in the war between the Allies and German U-boats in the North Atlantic. In Black May, noted historian Michael Gannon focuses on that single month to provide the first detailed account of the destruction wrought on the largest submarine fleet ever assembled in the Atlantic. Although the number of operational U-boats increased from 1942 through the spring of 1943, German losses and the rapid expansion of Allied forces took a toll on the powerful submarine force. As a result, in May the Allies destroyed 41 German U-boats and damaged 37.

Using excerpts from tapes of captured U-boat crew members; original documents from British, Canadian, German, and United States archives; and interviews with surviving participants, Gannon explains how the German sea defeat of May 1943 was more a culmination of events rather than a lightning-strike victory. These events allowed the Allies to deliver a crippling blow to the German U-boat force from which it never recovered.

Shelley Davis is a freelance writer from Virginia.