Asimov is known as a prolific author--but not particularly in terms of adult science fiction novels. Really, less than a couple of dozen--and he's best known for his Foundation and Robot novels. There was almost three decades between the first three Foundation books and Foundation's Edge. There he linked those two universes, Robot and Foundation. I read Foundation's Edge before this book written a few years later, and found myself liking this one quite a bit more. The reason is Elijah Baley and R. Daneel Olivaw and their partnership. Asimov is known more for his mind-expanding ideas and world-building than prose or characterizations. I can often remember the basic premise and pay off of his various novels--but rarely the characters, particularly by name. I finished reading Foundation's Edge only days ago, and already I'd have to go find the book to list the names of the central characters. That's not the case here--both characters have a voice, a certain depth and appeal that means they stayed with me--as did this novel even decades after a first read. Elijah Baley as an Earthman, a police detective with both brilliance and vulnerabilities trying hard to overcome fears and prejudice. Olivaw is a "humaniform" robot from a "Spacer" world where, unlike Earth, robots are common. He reminds me quite a bit of Data of Star Trek's Next Generation and was no doubt one of his literary ancestors. No doubt it helps this is the third outing with these two--I'd recommend reading The Caves of Steel and The Naked Sun first. And as a late novel Asimov obviously had a lot of fun dropping in references to earlier novels and stories--something that for a fan like me was quite fun--and more than fun Asimov makes you think about what it means to be human. And I quite like the mix of mystery and science fiction.