I've read about 2/3 of the Silo Saga and I can't second this recommendation enough. It was originally just a novelette, but it was so popular on Amazon that he

I've read about 2/3 of the Silo Saga and I can't second this recommendation enough. It was originally just a novelette, but it was so popular on Amazon that he was compelled to write more and so far, it's all excellent.