Manhattan ADA Butch Karp gets a crack at the crime of the century in this heavy-breathing addition to a popular series that includes such brainy thrillers as Depraved Indifference (1989) and Material Witness (1993). A congressional committee reopens the investigation into the assassination of President Kennedy, and Butch is tapped to lead it. Accompanied by his wife, tough-as-nails prosecutor Marlene Ciampi, into the Washington world of ambiguous allegiances and byzantine conspiracies, he soon stumbles onto ``Evidence of an interest on the part of the CIA to suppress a thorough investigation,'' a mysterious Guatemalan connection that suggests even darker doings in Castro's Cuba than were suspected all along, and the secret history of a JFK colleague and friend whose own nefarious agenda may have involved him in the crime. Faked photographs, altered identities, menacing look-alikes, and murdered witnesses litter the pages. It's apparent that Tanenbaum, who worked with the original congressional committee's investigation, has thought long and hard about the case over the years. But all this is a bit much even for the most devout conspiracy theorist. Furthermore, the Karps' tough- love relationship is becoming more than a bit mannered, and their habit of hurling bad puns at each other (``Give me lavatory or give me a bath'') takes us back to the days of Ellery Queen at his most self-consciously cloying. There's also far too much cutesy attention lavished on their precociously self-possessed moppet daughter Lucy. Here and there we get glimpses of Tanenbaum's virtuosic ability to sort out and dramatize complicated material, but this novel is sunk in its own self-importance.