A classic collection of robot stories, though I have to admit for me the attraction is often less the robots than it is Susan Calvin. I find her hugely entertaining, and it's always slightly disappointing when I come across a robot story that stars Powell and Donovan instead. The stories themselves are always enjoyable, and it's really interesting to delve into the psychology of robots - at least, the psychology of robots who are imprinted with Asimov's Three Laws. It's the tendency to instability in case of conflict that's the most fascinating, as I think is well illustrated in the best story of the piece, "Little Lost Robot". But in the runner-up story, "Evidence", is I think the flip-side: a stable robot, advanced enough, is plainly superior on every level to its human creators... even morally. That tension in the text never fails to give interesting results.