Yakir Aharonov is one of the pioneers in measuring theory, the nature of quantum correlations, superselection rules, and geometric phases and, as such, has made monumental contributions to theoretical physics. Together with Daniel Rohrlich of the Weizmann Institute, Israel, he has written here a groundbreaking work on the remaining mysteries of quantum mechanics. With both students as well as researchers in mind, the authors provide an insight into that part of the field that led Feynman to declare "nobody understands quantum mechanics".