The question is raised about the study of mosque books of the Tobolsk province of the XIX - early XX centuries, stored in the State Budgetary Institution of the Tyumen region “State Archives of Tobolsk”. It is reported that the documents cover the period from 1830 to 1917 and are the metric books of the Siberian Tatars “on a note on births, about marriage, divorce and death”. The relevance of the study is due to the preservation and study of the literary texts of the indigenous Turkic people of Western Siberia - the Siberian Tatars. A review of the geography and chronology of preserved manuscripts is carried out, the features of the composition of the information contained in mosque books of the Sauskan and Chebourg yurts are considered. The authors emphasize the value of metric books as a source, since some traditional features of Tatar writing of the 18th-19th centuries have been preserved in them, which is associated with generally accepted standards for the design of official business papers. The scientific prospects of the study are considered: the creation of a written corpus of manuscript books of Siberian Tatars; analysis of the unexplored literary texts in the corpus, archaeographic (paleographic description, the study of graphics, spelling and punctuation), linguistic-textological and linguocultural aspects; application of the genealogical approach in describing the anthroponymic of Tobolsk province of the 19th - early 20th centuries on the basis of metric data on births, marriages, divorces and death.