Surfacing / Margaret Atwood.

Enhanced descriptions from Syndetics:

From the bestselling author of The Handmaid's Tale and The Testaments-- this story of an artist who goes in search of her missing father on a remote island in northern Quebec is a provocative blend of literary mystery, psychological thriller, and spiritual journey.

Accompanied by her boyfriend and a young married couple, the artist searches her abandoned childhood home for clues her parents may have left. But in the disorienting, transformative isolation of the wilderness, her friends' marriage begins to crumble, sex becomes a catalyst for conflict, and violence and death lurk just beneath the surface. As her relentless probing leads to an electrifying confrontation with her own suppressed secrets, she rapidly descends into what could be either madness or the starkest self-knowledge.

Margaret Atwood's haunting masterpiece is permeated with suspense, complex with layered meanings, and written in brilliant, diamond-sharp prose.