Isaac Asimov’s Robot City: Robots and Aliens: Changeling
Despite the rather unwieldy name, and being trapped as the seventh book in a share cropping series using Asimov's name, this is actually quite a good book. The plot explores something Asimov didn't do much of (what happens when Asimovian robots meet aliens and define them as human), while not being self righteous about it. The book is also more technically competent that some of the earlier ones in the series -- it doesn't feel like it was written for seven year olds. I think this one is the best in the series so far.