This was a Hugo-nominee in 1962. Size is 5" by 7-1/2" by 3/4" thick. The only English-language hardcovers you can get of this book are British, and over 50 years old.

Long after a nuclear holocaust, the survivors' descendents live sightless far underground. One man defies the rule of his elders in search for the truth to his past. Jared faces severe penalties, but his desire for knowledge surpasses any punishment he might receive... [Dark Universe was a Hugo nominee in 1962.]