This introductory textbook on sociolinguistics the study of language in relation to the people who use it covers such topics as: the notion of dialect, the balance between individuality and conformity in language usage, the significance of pidgins and creoles and the attitudes evoked by languages and dialects.
This is not a new book and you notice it in many places. For example, when discourse structure is discussed (or left undiscussed) or in the chapter on quantitative study of speech which definitely needs a serious update. The book also seems a bit unfocused to me as it introduces many interesting topics but does not cover them in enough detail. For example, you'd better read about prototypes somewhere else (e.g., "Linguistic Categorization" by Taylor).
The book is pretty solid as an introduction. I particularly liked the chapter on linguistic inequality — something that I haven't seen in such texts (not discussed at such length anyway).
The book would have benefited from control questions after each chapter (it's an introduction after all), though. Also, most of the pictures are ill-made and quite hard to follow, even with the explanations in the text.