Consider reading translations of other epic poems, such as Vergil's Aeneid, Homer's Iliad and/or Odyssey, and The Epic of Gilgamesh. J.R.R. Tolkein's Lord of the Rings trilogy is also written in an epic style.
Also consider Grendel, a novel by John Gardner that retells some of the events of Beowulf from the point of view of the monster. Another good companion to Beowulf might be Joseph Campbell's Hero with a Thousand Faces, an anthropological text that discusses the concepts of myth and heroism in Western culture.
