A succinct overview with a good selection of examples and case studies, it has something for anyone involved with either linguistics or indigenous cultural survival.
Crystal begins by looking at the scale of the threat to minority languages.
None of these are likely to convince either aggressive monolingualists or the apathetic, but Crystal includes some thought-provoking details and quotes. Obviously a language dies if all of its speakers die as the result of genocide or natural disasters, or are scattered in such a way as to break up the language community. This process is broad and complex, but one major factor is negative attitudes to a language, both in government policy and local communities.