The Barrett family (Mom Sarah, dad John, big sister Marjorie, and little sister Merry) are doing just fine. Merry loves the time she spends with her sister rewriting the stories in her Richard Scarry books. Then Marjorie starts showing signs of mental illness. Her additions to Cars and Trucks and Things That Go get a lot more menacing. It doesn’t help that John has lost his job and the doctor bills keep adding up.

Advice from doctors and therapists isn’t working, so John turns to his long-dormant religious faith, and seeks help from a priest, Father Wanderly, despite Sarah’s misgivings. Together John and Father Wanderly determine that Marjorie has been possessed. Only an exorcism will save her. The only way to make ends meet is to allow a camera crew to document the whole thing for a new reality TV series, The Possession.

These ill-advised “solutions” just make the situation grow more and more frightening and disorienting, until we’re left wondering if any of this is real. Is Marjorie sick? Is she possessed? Is she playing a role designed to solve their financial troubles? Or is she attempting to call attention to a deeper problem within the family?

A Head Full of Ghosts is a novel that’s very, very aware of its influences. It is full of references to horror movies and books, some blatantly obvious, specifically name checked, and others more obscure, for only hard-core horror fans to notice. These references seem designed to nip in the bud any criticisms that the story is too derivative of other horror stories. Marjorie’s possession story does closely align with the now-cliched plots of The Exorcist, The Exorcism of Emily Rose, The Last Exorcism, and dozens of others.

But A Head Full of Ghosts isn’t really about an exorcism. It’s about the difficulty of discerning fact from fiction in the media, in our faith, in family relationships, and even in our own memories.