Entropy Beyond the Second Law: Thermodynamics and statistical mechanics for equilibrium, non-equilibrium, classical, and quantum systemsThe Second Law of Thermodynamics, that entropy increases, is arguably the most fundamental law of nature. And yet for some, entropy itself is a mystery, the cause of confusion and misunderstanding. How can it be that something so fundamental and universal be so hard to grasp? How can it have happened that thoughtful people appreciate the significance and universal applicability of the Second Law without understanding the nature of entropy, its sole