**** Jon Lellenberg: Baker Street Irregular, Arkham House/Mycroft & Moran, $39.95. The outstanding item in our annual birthday round-up is the latest novel about eminent fans of the Baker Street sleuth. Though it follows fictionalizations as excellent as Anthony Boucher’sThe Case of the Baker Street Irregulars (1940) and Arthur H. Lewis’s Copper Beeches(1971), this quite different novel may be the best of them all. In an espionage saga extending from 1933 to the early years of the Cold War, New York lawyer Woody Hazelbaker helps settle the affairs of mobster Owney Madden, joins the BSI, and participates in intelligence activities before, during, and after World War II. Clearly based extensively on fact (and a whole second volume is projected to document and clarify), this extraordinary historical novel is recommended to anyone interested in the run-up to World War II in the United States and the role of codebreaking in the defeat of Germany and Japan. Excellent talk in place of physical action gives a much more authentic feel than the cinematic choreography of lesser novels. Historical characters abound from FDR and Churchill to the founding Irregulars, many of whom (notably radio commentator Elmer Davis) had an important role in the war effort. Also appearing is prolific British thriller writer Dennis Wheatley, who would have appreciated how Lellenberg draws several plot strands together for a startling ending.