This edited volume gives an overview of the concepts and methods used in research in quantum logic, viewed both as an operational physical theory and in terms of purely mathematical structure. Far from being simply a collation of research papers, it consists of 11 specially commissioned essays that, taken together, provide both an introduction to quantum logic and an overview of research in this subject. The contributors discuss topics ranging from the algebraic theory of orthomodular lattices to recent applications of category-theoretic methods and connections with theoretical computer science. Moreover, an historical overview of the field and extensive citation and concept indexes are included.