Beowulf's novel and the movie begins the same way. Both begin with the arrival of Beowulf toDenmark to offer his help to Hrothgar to kill Grendel, a giant monster that devours human form to people in there to make noise.
Bewulfmanages to kill Grendel that night was to attack, but trusting in the death of Grendel everyone is quiet until one night Grendel's mother is going tokill all exept Beowulf. Beowulf will find Grendel thinking he was still alive but was the mother who had killed the other warriors and when itcomes to the cave where Grendel's mother was is where the novel difference because according to this Beowulf kills Grendel's mother but in themovie have sex with her and has a son after that Beowulf is king in Denmark because so decides Hrothgar king and suicide but according thenovel the king only gives honors and lands and even death of Herdred when Beowulf is king.
After 50 years of reign of Beowulf comes a dragon offire to the kingdom and the novel Beowulf fighting warrior and 11 more, but finally manages to kill him with a warrior named Wiglaf also dyingBeowulf to kill the dragon but the dragon in the movie is Beowulf´s son and Grendel's mother.
Apparently the novel is much longer than the movieand the novel has more characters than the movie. Also the novel is more story and the movie is more action to have more interest in the viewer.