The document provides an overview of David Crystal's book "English as a Global Language" which examines how and why English has become a global language. It summarizes Crystal's arguments that a language needs widespread use and recognition across countries to be considered global, and that English attained this status due to the historical spread and power of Britain and other English-speaking countries through colonization and immigration. The document also discusses some of the dangers Crystal raises of a single global language dominating, such as endangering other languages and creating linguistic complacency.