Hell House by Richard Matheson
Belasco House was a home of great horror and depravity in the early 1900s. Emeric Belasco had the windows bricked up so no one could see in and, more importantly, his guests could not see out. Cut off from the natural world, they lived a debauched life that descended into madness, eventually turning on each other in the most gruesome ways possible. He died and the people were cleared out but the house was still unlivable because it became haunted. Nicknamed Hell House, it attracted two groups of spiritualist (one in 1931 and another in 1940) to try and exorcise the house. Both groups went crazy within a week and killed themselves. The only survivor (from the 1940 group) was a hot-shot spiritualist teenager, Benjamin Fischer, who lost his powers after failing to change the house.
The novel Hell House starts in 1970 when another group comes to the house to discover and remove whatever forces lurk within. Fischer comes back for a second try. Florence, another psychic who has promising powers, also comes. They are joined by Dr. Barrett and his wife. Barrett has been studying psychic phenomena in a scientific way and plans to prove his theories about what really causes "hauntings." He has a bit of disdain for the psychics but sees them as necessary to spark activity in the house. They've all been promised a lot of money by the current owner of the house, Mr. Deutsch, who wants proof of an afterlife. Deutsch even fronts money to Dr. Barrett to build a machine that he needs to "take care" of the haunts.
Once ensconced in the house, the group has a few seances that bring out the typical "you'd better get out of here or we'll have to kill you" messages, which they are more excited about than fearful of. Tensions mount between the psychics and the Barretts. Their continued investigations bring some insights into each other and the house's history but also causes a lot of pain and danger. And ectoplasm!
The story follows some standard haunted house tropes (science vs. psychics, is that ghost really who they say they are, etc.) but the characters are interesting enough that I bought into the plot. The book is graphic in that way many books from the 1970s are (the novel Jaws springs to mind), giving explicit details both sexual and gory. The graphicness bothered me, but the book is a horror story. I probably won't shelve it where the kids can reach it. The book is an interesting, typical haunted house book.