"Wool" series by Hugh Howey.
This is a science-fiction trilogy set in the world of a "silo", a self-contained survival shelter buried deep underground and on the edge of a social breakdown. I've read a lot of SF&F, and can often guess how a story will develop early on, but this one kept me guessing! It's deep, multi-layered and has surprisingly rich characters for a plot-driven work. Certainly one of the most enjoyable page-turners I've read in recent years.
Striving to improve in every way possible.