Murder Beneath the Buried Sky by Keith Hartman
The plot centers around Calvin, trapped in a city in a cave, filled with people who originally moved into the cave around 15-20 (the time is kind of vague in this. Mind you, I assume this has to do with living in a cave with no natural light. Although that vagueness does become clear in the end.) years ago to escape "The Burn", the time when all the nukes got launched. Due to the radiation, the cave is sealed off, and geiger counters are positioned near the only exit so that when the radiation clears, the survivors can return and start working the Earth. Problem is, they really only planned to be in the cave for about 5 years. Calvin is the First Born, his mother having entered the cave pregnant. After 5 years, they ran out of birth control, and new kids were born.
As the book starts, we get a feel for the setting. Calvin lives in what once was a supply closet with 5 other boys. Which leads to a real lack of privacy, Particularly when one of his roommates brings home an older woman for vampire sex games. (I'm cheaply amused by this, since later on, he runs across them again, only this time the roommate is an Athenian slave boy and she's the Empress. Also, it's pointed out that most of the younger population of the cave and the adults for that matter, are functionally bisexual.) Anyway, as the story progresses, we find out Calvin's estranged father has been murdered, and Calvin is the prime suspect. And the ruling Council isn't inclined to give him a trial as much as kill him to get it under the rug. As the book goes on, it begins looking at issues with the situation, such as starvation as the Grow Lights start dying off, paranoia inherent in a closed, society, etc.
Anyway, as could be expected in a mystery, the ending brings resolution of a sort, as we, the readers find out what's really been going on beneath the Earth.
And in the notes, Mr. Hartman discusses that his inspiration for the whole thing comes straight from Plato's Allegory of the Cave. Although really, it shares common themes with The Matrix, The Dome, Logan's Run, and even Crowley's Book of the Law. Basically, once again, the idea that someone finds knowledge, tries to return with it, and instead gets attacked by people who either don't want to believe or can't cope with it.
All in all, a very good read, and highly recommended, particularly if you're one of the 20 people who read his other books.