Hobgoblin

Hobgoblin is a 1981 Problem Novel by John Coyne which follows Scott Gardiner, a player of "Hobgoblin", an Irish-themed Role-Playing Game as he deals with the death of his father, his mother's new job documenting the history of Ballycastle, and dealing with a new school.

Tropes used in Hobgoblin include:

Badass Grandpa: Conor and Fergus are easily in their 70's, but a lifetime of menial work still lets them wreak havoc with medieval weapons when they wish to.
The Blacksmith: Conor's role at Ballycastle is to restore the items therein including the weaponry.
Broken Aesop: The epilogue of the story implies that Scott's obsession with Hobgoblin was a childish thing which he's since put aside upon starting college. On the other hand, it was skills associated with the game that let him fend off Fergus when he returns and goes on a killing spree.
Jerk Jock: Borgus and his crew.
Knight in Sour Armor: Scott doesn't so much want to save the high-schoolers as that he's less than sane at that point.
Loners Are Freaks: Played with to some degree. Scott wants little to do with the town of Flat Rock and it's portrayed as unhealthy. However, they wanted nothing to do with him either.
Ripped from the Headlines: The book was put out at the same as Mazes and Monsters to ride upon the Moral Panic of the Egbert incident.
There Are No Therapists: Averted. Scott sees a therapist both after his father's death and after killing the rampaging Fergus.