The introduction to Language Learning and Leisure provides two reviews of the literature in this area, overviewing first the field to date and second the contributions to the book itself. We begin with a short etymologically-based explanation of the choice of title of the book and a brief history of the genesis of the volume. The review of the field to date examines literature touching on informal or leisure-related language acquisition since the early examples in the 1980’s and 90’s. It analyses past publications according to five categories: what informal language learners do, where they do it, the prevalence of English, what is learnt (language development) and the relationship of informal and leisure learning to other types of learning. The presentation of the contributing chapters follows the organisation of the book, presenting the nature of informal second language learning and informal second language learning research, research into language outcomes, learner activities and strategies, psychological dimensions of informal second language learning and more specifically engagement.