Only a few of the 25 oddly-assorted pairs gathered here are romantic couples (Kelly Roos's Jeff and Haila Troy, Julie Smith's Skip Langdon and Steve Steinman); more often, they're colleagues professional (P.G. Wodehouse's Paul Snyder and Elliot Oakes, R. Austin Freeman's Thorndyke and Jervis, Lawrence Blochman's Dr. Coffee and Dr. Mookerji, Michael Gilbert's Calder and Behrens, Reginald Hill's Dalziel and Pascoe, Edward Hoch's Sebastian Blue and Laura Charme, editor Muller's Rae Kelleher and Sharon McCone, editor Pronzini's Sabina Carpenter and John Quincannon, Barbara D'Amato's Suze Figueroa and Norm Bennis) or quasi-professional (Margery Allingham's Campion and Inspector Kenny, Stuart Palmer and Craig Rice's Withers and Malone)--or they're Holmes-and- Watson pairs (Hulbert Footner's Mme. Rosika Storey and Bella, Ellen Dearmore's Gertrude Stein and Alice B. Toklas). Though there's some history here (Patrick Quentin's first Peter and Iris Duluth story, the Lockridges' only story about Pam and Jerry North, Fredric Brown's only story about Ed and Am Hunter), most of the selections (e.g., Dorothy Sayers's ``The Footsteps That Ran,'' Agatha Christie's ``The Love Detectives,'' Rex Stout's ``Fourth of July Picnic'') are typical rather than distinguished. And does anyone really need yet another copy of ``The Purloined Letter'' (featuring the most featureless Watson in the business) or ``The Adventure of the Empty House''? More dutiful than inspired despite its range of duos: a missed opportunity for the editors--the genre's own reigning First Couple--and their readers.