Burnt Offerings by Robert Marasco

Ben and Marian Rolfe are desperate to escape a stifling summer in their cramped and noisy Queens apartment, so when they get the chance to rent a mansion in upstate New York for the entire summer for only $900, it's an offer that's too good to refuse. There's only one catch: behind a strange and intricately carved door in a distant wing of the house lives elderly Mrs. Allardyce, and the Rolfes will be responsible for preparing her meals.
But Mrs. Allardyce never seems to emerge from her room, and it soon becomes clear that something weird and terrifying is happening in the house. As the suspense builds towards a revelation of what really lies behind that locked door, the Rolfes will discover that their cheap vacation rental comes at a terrible cost . . .
The basis for a classic 1976 film adaptation and an acknowledged influence on Stephen King's The Shining, Burnt Offerings is one of the most original and scariest haunted house novels ever written. This edition, the first in decades, features a new introduction by award-winning author Stephen Graham Jones.