Almost did 4 stars. This one just wasn’t as good as the others in the series - a lot of the neat concepts that Asimov explores in the others is subsumed to the plot, which is plodding. But, it ends very well. I confess I did not see the answer to the puzzle in front of Baley until the last pages spelled it out, and it ties the world into the later books. So, yes, I would still recommend it.