This breezy, gossipy, beautifully written book traces the early life of the writer Roald Dahl as he made the rounds and unmade the beds in 1940s Washington as one of His Majesty’s dashing spies. Intent on bringing the United States into World War Two, England established a clandestine agency called British Security Coordination, which undercut American isolationist sentiment and monitored domestic politics. For talent, BSC looked to men like Dahl and Ian Fleming, who had good ears and clever conversation. With his polished brass buttons and natural swagger, Dahl encouraged glamorous confidences over morning tennis with the vice president, at poker with Senator Truman, and in bed with actresses, heiresses, and congresswomen (a friend crowned Dahl “the biggest cocksman in Washington”). While Franklin, Eleanor, and the Hyde Park weekend set contemplated another dip in the pool before cocktails, Dahl was “scribbling notes on the backs of matchbooks and dinner napkins” and also writing his first short stories. He reported to William Stephenson (code name Intrepid), the BSC chief whom author Jennet Conant apparently admires but whose secrecy and ferocious territoriality call to mind Dick Cheney’s one-lipped snarl. Conant’s narrative is so effortless and entertaining that the reader largely forgets the war that raged while Dahl drank champagne and penned silly letters impersonating the ambassador. Nevertheless, it’s hard to suppress a mild discomfort with a story about back-slapping, there’s-a-good-chap intelligence antics when our own spies these days are doing things we’d rather not know about. The book also chronicles one too many a divorce, showing that dish about the private lives of yesterday’s or today’s celebrities is pretty much the same thing, and always a little distasteful. But the latter objection also applies to the latest steamy romance novel, and so does this rejoinder: deep down, we love the stuff.