At first glance, it's a 1,000-page, detailed biography of a (in)famously effective city planner Robert Moses. At its core, it's a lucid examination of the anatomy of power. It has completely changed how I think about power, where it comes from (whether it's at work or in the greater market/world) and how it is retained and lost.
It's also a great antithesis to junk-food journalism and online reading that we've become addicted to. Caro's research is thorough and his writing is inspiring.