The book is about history of Lithuania and Russia in Medieval Ages, about writing chronicles, and meanings of words used at the time. It is an analysis of over 30 volumes of the Full Collection of Russian Chronicles, that dates back to 855 A.D. The chronicles in Medieval Ages were written in Slavic using Cyrillic alphabet by monks of the Russian Orthodox Church and in Old German and Medieval Latin by monks of the Teutonic Order. Full texts from Lithuanian in Old Belorussian tongue and excerpts in translations from Russian and Teutonic are included.

The book starts in 13th century Lithuania—the time Lithuania emerged as state. The analysis of chronicles takes its reader through said above records made by Russian Orthodox monks (855 - 1453 A.D.), and to records and documents made by Catholics—Teutons and Poles (1191 - 1434 A.D.), Lithuanian (1345 - 1446), and ends with remarks about errors in dictionaries. The book describes the order in which chronicles were copied and therefore contains solutions to unsolved problems of sequence. The book contains graphs, tables, maps, that clarify explanations, a dictionary with almost 2200 entries and an Indices of Names, Tribes, Geographical Places, in which the Author provided extended information about the people, tribes, and places.