A HEAD FULL OF GHOSTS Review: Want To Be Scared This Halloween? Read This.

Paul Tremblay's maybe-possession novel will scare you sideways.

I finished Paul Tremblay's mostly Boston-set A Head Full of Ghosts while in Boston this weekend, flying through the last couple hundred pages like I had something to prove. I finished it in bed, fell promptly asleep and woke up after one of the gnarliest nightmares I've had since I was a kid prone to such dreams. I had to wake up my husband and turn on the light - it was that kind of nightmare. 

But hey, don't take my word for it. For all you know, I'm a wuss. (I'm no wuss.) Here's a guy you can trust:

So what is it about A Head Full of Ghosts that is so deeply, elementally frightening? Tremblay follows a small-town New England family called the Barretts: dad John, recently unemployed and newly enthusiastic about religion; mom Sarah, the terse, chain-smoking breadwinner with little patience for John's born again rantings or much else; unnervingly smart 14-year-old Marjorie, who's just reaching that age where privacy is everything; and our narrator, 8-year-old Merry (short for Meredith), who worships her big sister and sees more of what's going on with her family than her parents would ever suspect.

Her second year into teenagerdom, Marjorie begins exhibiting signs - at first subtle, and soon terrible - of schizophrenia, alarming her parents and terrifying her little sister. John, under the guidance of the inscrutable Father Wanderly, becomes convinced that she's possessed, and as Marjorie's episodes grow in scale and horror, he soon wears down Sarah into agreeing to submit to the church's control. The Discovery Channel offers a seductive amount of money to the struggling family to film the proceedings, and a show called The Possession is the result - a reality television program that garners a fervid cult following, as well as a group of hateful, picketing zealots and a lot of unwanted attention for Merry and Marjorie.

There are a couple of framing devices around A Head Full of Ghosts' central story: one is the blog The Last Final Girl, with a horror-obsessed young woman named Karen revisiting with insight and exactitude the six-episode TV series a decade and a half later, and one following a now 23-year-old Merry as she's interviewed by a writer investigating the story as a cold case. Neither of these framing devices - both compelling in their own way - creates any distance from young Merry's horrifying story, however, which feels as immediate and tangible as our own blackest memories. Marjorie's illness, the tension between her parents, the strangers invading her home with cameras and lights and microphones, the new and unwanted pressure by her father to believe in something she knows little about - Merry internalizes it all, a small girl who cannot change her world but absorbs everything that is wrong with it.

The scares are scary, very scary, and it's a book written by a horror fan for horror fans. There's a deep and very modern knowledge of horror running through this story - the Barretts don't exist in a world ignorant of such films as The Exorcist and The Amityville Horror - nor The Conjuring, Evil Dead or Session 9. The references grow less obvious: Burnt Offerings and Sara Gran's Come Closer are both name-checked in an organic way. Charlotte Perkins Gilman's "The Yellow Wallpaper" is pivotal to this story, as the religious patriarchy locks a teenage girl in her room and refuses to let her out until she can at least feign a life that hews to their particular strictures. 

The adult Merry loves horror, as does The Last Final Girl's Karen, whose knowledge is vast and pinpoint-applicable to the events she's viewed onscreen dozens of times since her favorite show first aired. And the book is self-referential in a way that only feels aware, and not in the least ham-handed. Karen says of The Possession's subtle horror references: 

Again, I think this is another brilliant bit. The show had horror fans hooked at hello because, frankly, most of us are not picky. We're like the family dog that wags its tail at a treat, no matter if it's a crappy store-brand Milk-Bone or a piece of steak. We (yes, I'm still speaking for you, horror hound) don't mind the familiar and recycled as long as we can consume it without gagging. To the general populace, the recycled bits of classic horror might be naggingly familiar in some recesses of their pitiful and atrophied culture-lobe of their brains (mmm, braaaaiiiins!!!), but to them it plays as totally fresh and new, and frightening.

Of course, A Head Full of Ghosts could be speaking about itself here, playing to horror fans with its heavy references but also placating the "general populace" who might pick up this family drama unsuspectingly. And if Karen's blog voice makes you wary (I love it; it feels completely accurate to this girl who once had her own horror blog that no one read), know that it's only part of the narrative. We have older Merry's voice, and most compellingly, the voice of young Merry, who doesn't like sauce on her spaghetti noodles and who draws "a pair of blocky, black-framed glasses" like her own on all of the characters in her Richard Scarry books. Merry couldn't feel more real if she were our own little sister, or if she were us. With her ineffectual parents and sick sister, Merry is left to fend for herself, and she does so admirably, in the most badass eight-year-old way possible: 

With each passing minute that she didn't come into my room, I grew more frantic and paranoid and convinced that she was indeed coming. So I rigged my bedroom to try to catch her in the act. Wouldn't she be in trouble with Mom and Dad then, given how much of a surly-teen stink she put up whenever I went near her room. I took the belt from my fuzzy purple robe that I never used and tied the ends to a bedpost and the doorknob. The belt had just enough slack that my bedroom door opened so only someone my size could wiggle safely through. I also balanced an empty plastic orange juice jug on top of the slightly open door frame. If the door opened beyond the constraints of my robe belt, the jug would crash to the ground, or better yet, on the door opener's head. No way would Marjorie sneak in without getting stuck or making enough of a ruckus to be heard by me.

I didn't feel 100 percent safe so I built motion-detecting surveillance cameras and a laptop computer out of cereal boxes. I spent Sunday morning conducting quite a few background checks on one Miss Marjorie Barrett. Oh, the things I found.

With all of its peculiar delights, by far the most affecting part of A Head Full of Ghosts is this central relationship between sisters. Marjorie and Merry have always been close, sharing stories and secrets, tiny details that make A Head Full of Ghosts feel impossibly real, but the thing inside Marjorie - a demon, or just a straightforward illness - becomes single-mindedly preoccupied with Merry. Marjorie's most terrifying episodes are in Merry's presence, and she focuses on the little girl - toying with her, taunting her, but also desperately needing her - in a way that makes Merry terribly important to the looming exorcism, and to The Possession's ratings. Merry wants so badly to help her sister, to trust her, to believe the heinous things Marjorie tells her rather than believe her big sister is lying to her. Their relationship is beautiful, and bad, and completely consuming. They are co-dependence writ large, their need for each other - particularly Marjorie's need for the young Merry, who can only be so strong for her troubled older sister - turning dark and dreadfully heavy, too heavy to carry.

A Head Full of Ghosts is many things: an examination of the push-pull between religion and science and our need to be saved by one or both, a devastating family drama, a very scary horror novel, but mostly it's a story about two sisters, one big and one little, and the way their love for each other sustains them and chips away at them at once.