This book synthesizes and integrates 40 years of research on the semantics of questions, and its interface with pragmatics and syntax, conducted within the formal semantics tradition. A wide range of topics are covered, including weak-strong exhaustiveness, maximality, functional answers, single-multiple-trapped list answers, embedding predicates, quantificational variability, concealed questions, weak islands, polar and alternative questions, negative polarity, and non-canonical questions.