Background
Herberstein's knowledge of Slovene, acquired in his youth, allowed him to communicate freely with Russians, as Slovene and Russian both belong to the Slavic languages. He used this ability to question a variety of people in Russia on a wide range of topics. This gave him an insight into Russia and Russians unavailable to the few previous visitors to Russia.
He probably wrote his first account of life in Russia between 1517 and 1527, but no copy of this survives. In 1526 he was asked to produce a formal report on his experiences in Russia, but this remained relatively unnoticed in the archives until he was able to find time to revise and expand it, which he possibly started in the 1530s.
The evidence suggests that Herberstein was an energetic and capable ethnographer. He investigated in depth both by questioning locals and by critically examining the scarce existing literature on Russia. The result was his major work, a book written in Latin titled Rerum Moscoviticarum Commentarii (literally Notes on Muscovite Affairs), published in 1549. This became the main early source of knowledge in Western Europe on Russia.