In “The Knowledge” by Martha Grimes, Richard Jury investigates the shooting of an American physicist and his wife outside a swank London casino.  In “The Glass Room” by Ann Cleeves, Vera Stanhope finds herself in an Agatha Christie style  mystery where someone is murdered at a country house and all the guests are all suspects.   “Twenty-one days” by Anne Perry finds Daniel Pitt under the clock to exonerate an author for the alleged murder of his wife.  Closer to home, “Hard Aground” by Brendan DuBois finds Lewis Cole confined to his Tyler Beach home after surgery–until a case comes knocking. And in “Old Black Magic,” an art theft thrusts Spenser into the shady world of black market art dealers.  Standbys Vinnie Morris and Hawk lend a hand while author Ace Atkins (pinch-hitting for the late Robert Parker) provides the quips.