The proposed article presents the analysis of the historical research of A.L. Shletser on the problem of the heritage of Cyril and Methodius in Rus’. The historian raises a question of Slavonic church books
as historical documents, but he didn’t conceptualize them as the products of the mission of Constantine and Methodius, as the heritage of Cyril and Methodius in a broader historical context.
Key words: A.L. Shletser, Cyril, Methodius, the heritage of Cyril and Methodius in Rus’, Cyril and Methodius studies.