Although I read plenty of "adult" SF and many other categories of books as well, one of my favorite genres is science fiction that's intended for young readers. And for some reason, many of the books I like are in the post-apocalyptic SF sub-genre, i.e., plucky kids trying to save or rebuild the world after war, alien invasion, or some other disaster. Ender's Game is a prime example, and also John Christopher's Tripod Trilogy (starting with The White Mountains). Another favorite is The Last Book in the Universe by Rodman Philbrook.
I won't try to psycho-analyze why I like these books so much, but I just found another really good one, The City of Ember by Jean Deprau. I bought it some time ago, but just happened to spot it on a shelf this week. This was a fortunate procrastination, because in the meantime, the sequel The People of Sparks came out, and I bought and read that too. Ember is an underground city powered by an underground river that drives a huge generator. It was created by "The Builders" and stocked with a 200 year supply of goods to preserve a small group of people in the wake of a series of world-wide disasters that have destroyed most human life. An essential (though somewhat odd) plot element is that the Builders elected to keep most knowledge of human history and technology from the people of Ember, providing them with just what is needed to survive, plus a concealed set of "egress instructions" which of course are lost. I won't give away the plot, but the fact that there is a sequel suggests that the young people do finally save the day.
There's no direct space connection here, except that this isolated and self-sufficient (until the generator fails) community of some 500 people living in a fairly small place made me think of the problems that future groups of Mars or other space colonists will face. The sequel explores the nature of conflict and the problems of resource allocation and social responsibility in difficult situations. It's light reading, but thought provoking too.