Science fiction with real emphasis on science (and philosophy); Asimov ponders -with great insight- on his favourite theme, robots and artificial intelligence, but also on overpopulation, space colonization, future social structuring etc., by using the narrative of a detective story, in something that is in some ways a parody of the classic hard-boiled/noir variation. Despite it's a little rough at the edges literature-wise, it still is a great work that now is entertaining also because we can see what things that Asimov "predicts" have already happened and what other ones have taken a totally different route.