According to Wikipedia, Asimov considered this his worst novel. I can see why. It's not aged particularly well (which isn't his fault, of course). While the story itself has its moments, two things really lowered my evaluation. First, the casual sexism on display is really hard to ignore - there's one woman in the whole book and she exists only to provide a love interest for our hero. Second, the ending is a complete howler. To be fair, it wasn't Asimov's idea, but it's still his name on the book, so he gets the blame. Thankfully, he'd go on to do much better.
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