The central concern of this book is the analysis of verbal interaction or discourse. This first six chapters report and evaluate major theoretical advances in the description of discourse. The final chapters demonstrate how the findings of discourse analysis can be used to investigate second-language teaching and first-language acquisition and to analyse literary texts.
He's the best in introducing discourse analysis. Johnstonne is good, but not as organized as Coulthard. He divides the possible analysis from conversational analysis, etnography of speaking, stylistics, and even language teaching. He even makes me realize that tones and paralinguistic elements are also important for discourse analysis.
You need to have had read other introductions to be able to make sense of the first page of this introductory textbook. It is comprehensive but my class did not really find it introductory.