Eaters of the Dead
Eaters of the Dead takes elements of the Anglo-Saxon epic Beowulf and the Arab Ibn Fadlan's account of his journeys among the Rus, and works them into a thriller. The historical detail is handled reasonably well, the story is fast-paced and gripping, and the contrast between the Arab/Islamic and Viking cultures is effectively exploited. The result may not be a great novel, but it's an entertaining one and should appeal to those interested in the period. Neanderthal survival into the modern era is a bit of a stretch, but no more so than the science in Jurassic Park.

The movie based on Eaters of the Dead is called The 13th Warrior.