THE LAST SPENSER NOVEL COMPLETED BY ROBERT B. PARKER　 With Sixkill, the thirty-ninth novel in the venerable, bestselling Spenser series, the Boston P.I. meets Zebulon Sixkill, a young man whose lack of discipline is more than made up for by his quick way with a gun. Though this is the last Spenser novel Parker completed, readers will rejoice to find the tough-but-tender gumshoe at his rogui...