The "Handbook on Approval Voting" explores the history, theory, and practical applications of approval voting. It discusses how approval voting was used in ancient Sparta and its implementation in modern elections. The handbook covers topics like committee selection, strategic voting, computational aspects, and behavioral differences between approval and plurality voting. It also includes insights from laboratory and field experiments on approval voting, as well as its impact on electoral competition and policy moderation. Overall, the handbook highlights approval voting as a valuable tool for understanding individual preferences and societal choices.