The mythic monster felled by Beowulf is re-imagined in John Gardner's novel, Grendel.
A fabulous resource is The Grendex: An index to the novel
Here is the Audio Book divided into Chapters
(this link will take you to a YouTube account page with the chapters)
This is an animated story released in 1981 covering the ancient legend of Beowulf, as narrated in a Monty Pythonesque way by Grendel (Sir Peter Ustinov), the "monster" in the legend.
IMBD