Hell House by Richard Matheson
Trade Paperback. Recommended!
Rolf Rudolph Deutsch is going die. But when Deutsch, a wealthy magazine and newpaper publisher, starts thinking seriously about his impending death, he offers to pay a physicist and two mediums, one physical and one mental, $100,000 each to establish the facts of life after death.
Dr. Lionel Barrett, the physicist, accompanied by the mediums, travel to the Belasco House in Maine, which has been abandoned and sealed since 1949 after a decade of drug addiction, alcoholism, and debauchery. For one night, Barrett and his colleagues investigate the Belasco House and learn exactly why the townfolks refer to it as the Hell House.
Hell House is the scariest haunted house novel ever written. It looms over the rest the way the mountains loom over the foothills. -- Stephen King