It's science fiction with some marvels of engineering. The story follows the destruction of life on earth and what comes afterwards (which is more than what you'd think after the destruction of life on earth). It's a multi-generational epic, touching on a few "historic" points in the timeline. There are marvels of engineering. There are awful people (the reason we can't have nice things).
Remember back when my website got zapped for a few weeks? The good news is that it was mostly backed up. The bad news is that my draft blog posts weren't backed up. Maybe I had a wordier book report prepped? Anyhow, now it's months since I read this book and I don't remember so much. Sorry!