Eaters of the Dead by Michael Crichton
In 921 AD, Aḥmad ibn Faḍlān ibn al-ʿAbbās ibn Rāšid ibn Ḥammād was sent from Baghdad as ambassador to the Volga Bulgars (who lived in the boundaries of modern Russia) to help establish Islamic law for the newly converted nation. The short journal he kept of his travels is famous for its descriptions of the Volga Vikings, in particular the death rites of one of their chietains. In Eaters of the Dead (1976), the fourth novel published under his own name…