A book by the famous linguist L. P. Krysin reveals the essence of the concept of «sociolinguistics», analyzes current terms, problems and directions of this science, talks about the origins of its study, determines the status and place of this branch of humanitarian knowledge in the circle of philological and extralinguistic issues of the XXI century. In the review special attention is paid to the expansion of the conceptual range of sociolinguistics in connection with the change in the communicative situation, such phenomena as the language code, variability and norm, literary standard and dialect, vernacular and jargon are studied. The social aspect of speech communication is considered. The marking of language units and models is indicated. It is noted that the author of the book interprets precedent phenomena and ethnostereotypes in their linguistic expression in a new way. The importance of observing speech norms in written and oral speech is emphasized. The facts of a living language and behavioral tactics that stimulate the creation of variable forms and sociolects are analyzed in detail. The question about the representation of non-normative lexemes in the «Explanatory Dictionary of Russian colloquial speech» is raised. The social and communicative system of the Russian language is described. The bibliography of the works of the Moscow School of Functional Sociolinguistics is given. The conclusion is made about the stylistic heterogeneity of language expression, the need to study, evaluate and classify the facts of the manifestation of the socio-culture of speech. The task is to increase the competence of native speakers and tolerance in communicating with representatives of different ethno- and socio-groups.