Eaters of the Dead by Michael Crichton is a hybrid of truth and fiction, with the first half recounting Ibn Fadlan's account of the Norsemen in Russia and the second recounting how he was carried to Denmark to battle the Wendol, who are heavily indicated to be residual Neanderthals. He eventually found peace with them until he was captured by King Niels and taken to Copenhagen where he was given an estate and ordered to fight Wendols every year on St. John's Eve at a duel called "The Meeting on the Ice". He fought the Wendols for eight years before making peace with them. He then tells his story to a priest, who records it for future generations. Although he does not name names, he clearly indicates that he is talking about the Norsemen when he says "So I went to Russia". He also mentions "the Emperor" which can only be reference to Vladimir II Monomakh who ruled from 958 to 1015. Finally, he describes the Wendols as "those who remained behind", which would include the Neanderthals. So yes, the Eaters of the Dead are real and they still exist today in Scandinavia. They are known as Wendol after their language which was similar to Latin but different enough to be considered its own language family. The name Fadlan comes from the Arabic word for "fanatic" or "extremist".