Mickelsson's Ghosts

Mickelsson's Ghosts is a 1982 novel by John Gardner, the last novel he wrote.

from the back of the book:

It is the story of Peter Mickelsson, a brilliant professor of philosophy, who, having totally lost control of his life, buys and sets about restoring an old farmhouse, only to find that he is haunted by the ghosts of former occupants.

He's not haunted only by ghosts of the house's former occupants, but by ghosts of his own imagination and weird happenings. Philosophy, psychology, religion, questions about madness and reality, abortion, the I.R.S., medical malpractice, incest, suicide,...

The New York Times concludes it's "a standard-brand thriller with a queer Gothic hum in the background."