What are the books that have shaped your thinking most?

I return often to Parkinson's Law, which is a very quick read and enormously practical. The Lessons of History by Will and Ariel Durant is probably the densest high-quality book in existence for its length. James Burnham's The Managerial Revolution and The Machiavellians are both fantastic and surprisingly relevant today. And I keep copies of Meditations by Marcus Aurelius in most rooms I spend time in. I know stoicism is slightly out of fashion right now, but it remains a lifelong guide for me.