This revised second edition is a comprehensive overview of why we speak the languages that we do. It covers language learning imposed by political and economic agendas as well as language choices entered into willingly for reasons of social mobility, economic advantage and group identity.
A good introductory read if this topic is something that interests you. However, I would have liked to see more attention given to ecological language planning perspectives. As it is, there is only one chapter for endangered languages and I feel it fails to capture the essence or importance of ecolinguistics. It's a dense read, with a lot of history discussed, but serves its purpose overall.