Ibn Fadlan lived 400 years too late to have meet the historical Beowulf, if such a man lived, because, due to the dating of a raid on the Franks mentioned by Gregory of Tours in which Hygelac died and Beowulf was saved only by swimming across the Rhine, the events of Beowulf take place around the end of the 5th century and the beginning of the 6th. However, this is a novel not a history, although Crichton wrote it as though it were an annotated translation of Fadlan's report of his journey north. He even includes a bibliography at the end of the novel, with a caveat: "the references in this afterword are genuine. The rest of the novel, including its introduction, text, footnotes, and bibliography, should properly be viewed as fiction."
He goes on to say " When Eaters of the Dead was first published, this playful version of Beowulf received a rather irritable reception from reviewers, as if I had desecrated a monument. But Beowulf scholars all seem to enjoy it, and many have written to say so." I can believe that. Crichton was following an time honored tradition of retelling an old story to an audience that no longer believes in dragons and ogres or that swamps are the abode of demons. If you are too lazy to read the book, the movie is a good substitute - "The Thirteenth Warrior" - but I really recommend the book. It was not too taxing, I consumed it in a day.