Norby: The Mixed-Up Robot is followed by several sequels. Whether the series will continue or not after Isaac Asimov's death is not certain as of the time of this writing, but the idea for the series was Janet Asimov's, and she is a skilled writer, so there is hope that there will be future Norby books. Each book in the series features a humorous adventure, with increasing sophistication of plot and characterization. For example, in Norby and the Queen's Necklace, Norby and Jeff travel back in time, mixing history up, and possibly changing the course of history by becoming involved in events that would lead to the French Revolution. In the most recent novel, Norby and the Court Jester, the evil Ing makes a mess of Jeff and Norby's vacation plans, and the duo, with the help of Admiral Yobo, have to save the planet Izz...