This third book on Quark-Gluon plasma and heavy ion collisions follows the previous ones, published in 1988 and 2005, that described theoretical proposals for a large program, and then the QGP discovery at RHIC.The present one describes the rather mature field, with extensive program at RHIC and LHC colliders and corresponding theory. QGP turns out to be a strongly coupled medium made up of quarks and gluons, existing in exploding fireballs. It is the hottest form of matter created in a laboratory. Other subjects discussed in the book are QCD vacuum structure, including topological solitons and nonperturbative phenomena. It also includes some recent progress in theory of hadrons, bridging hadronic spectroscopy with partonic observables.