A Head Full of Ghosts by Paul Tremblay

Published by William Morrow, 304 pages, $26

In this mind-bending book, reality has as many layers as a piece of phyllo pastry. An interview forces 23-year-old Merry to look back at her experiences as an 8-year-old. Back then, her 14-year-old sister, Marjorie, seemed to be showing signs of either schizophrenia or demonic possession. Or maybe she was just eerily wise to unwelcome truths in her family and cleverly using her disturbing outbursts to call attention to them. In any case, doctors didn’t seem to have any answers, so their religious father turned to a local priest. Father Wanderly thought an exorcism was in order—but he also invited a reality show to film the family drama.

At times Marjorie’s craziness seems like a well-crafted fiction, and there are moments when she seems pretty normal, which is equally unnerving. But then she’ll share a convincing vision of weeds and roots strangling the world, or tell Merry that she’s going to yank out her tongue and wear it as a necklace. And how to explain the moving furniture Marjorie seems to have manipulated? Her chatty blog mocking the TV coverage adds another dimension, prompting the question “What’s real?” all the more. And the suspense builds until Tremblay, a master puppeteer of truth and lies, much like Marjorie, takes us to yet another unexpected place of horror.

From page 219: Father Wanderly repeated his instructions. “To all present, please respond with, ‘Lord have mercy.’ ”

Marjorie said, “But later when he invokes the name of a saint you’re supposed to say ‘pray for us’ after each one. Merry, if you don’t do this correctly, you’re going to get a demon inside you, one that has pointy scales and sharp horns, and then you’ll be in hell, like me.”