I believe John Gardner gave the book this title because it is short and describes the same character. The word Grendel itself sounds like a monsters name and makes you picture it in your head what Grendel actually looks like. When you think about monster's you usually think about heroes also, so John Gardner wrote the story to make you think about Grendel as the monster, so in your head you can think about what the hero has to be capable of in order to slay or defeat the monster.
The story is set in Grendel's twelfth year of attacks. Grendel encounters a ram, the ram doesn't pay attention to Grendel and it upsets him. So Grendel throws rocks at the ram and stomps the ground, but the ram just stares at him, this reminds Grendel that Spring is almost there. Spring has begun and Grendel is angry and can't resist it any longer, so he heads for the mead hall where he kills Hrothgar's men and takes the bodies into the woods, where he eats them. This is the twelfth year of Grendel's war. Then the story takes a turn and goes back to Grendel's childhood, where it talks about how he found a way out of his cave, and was following a calf. When he tried to kill it a bull protected it, and charged at Grendel. Grendel soon made his way up a tree where the bull only could injure his leg. Grendel went to sleep in the tree that night, only to awake to find the bull was gone, but a group of men were approaching. The men hesitated at first, but then attacked Grendel. Grendel's mom soon arrived and all the men scattered. From this point on the story builds up until it reaches the twelfth year of his attacks again.
Grendel- He is a intelligent monster, that isn't sure about the world around him, but is very curious about everything he encounters. He lives with his mother in a cave underneath a swamp. He in many ways is likeFrankenstein?. The world around him doesn't accept him, so he feels left out and feels no ones respects him.