Instruct: Classify Amazon reviews into positive or negative sentiment
Query: The Ultimate Glimpse into Kievan Rus

This book was published in the 1940's, but was then renewed in 1976. While it is a bit outdated, the information that's found in the book is astonishing. Nearly every apsect of Kievan Rus is here: history, ways of life, systems of status, etc. And while the author Vernadsky does add his own opinions in only a few spots, the book is still very unbiased. So this is an excellent introduction of Medieval Russian history (another is the first half of "Land of the Firebird" by Suzanne Massie.).