A large, 17-entry collection of original stories, compiled by a longtime Asimov collaborator, to celebrate Isaac Asimov's first 50 years (1739-89) as a published writer. Each of the stories here is set in one or another of Asimov's invented worlds. Thus, in the mystery department, Edward Wellen proffers a new story about Asimov's eccentric near-future detective, Wendell Urth, while Edward D. Hoch pens a new Black Widowers tale. Science-fictionally elsewhere, Connie Willis writes a waggish yarn in which an aging Asimov is petitioned by the robots to repeal the Three Laws of Robotics; Pamela Sargent contributes a new tale of detective Lije Baley and the Caves of Steel; Orson Scott Card weighs in with a novella about the establishment of the Second Foundation; while Harry Turtledove and George Zebrowski contribute stories set in other Foundation epochs. Mike Resnick, Robert Sheckley, and Harry Harrison contribute new robot yarns, and still other variations emanate from Robert Silverberg, George Alec Effinger, Barry N. Malzburg, Sheila Finch, Frederik Pohl, Poul Anderson, and Hal Clement. No standouts--indeed, often disappointingly feeble: a case of self-congratulations all around.