The Empusium by Olga Tokarczuk

BookBar says: The Nobel Prize-winning author of Drive Your Plougs Over The Bones of the Dead and Flights returns with a horror set novel set in a spa retreat for tuberculosis sufferers, which riffs on Thomas Mann's The Magic Mountain. Fitzcarraldo lovers, this one's for you.
 
In September 1913, Mieczyslaw Wojnicz, a student suffering from tuberculosis, arrives at Wilhelm Opitz’s Guesthouse for Gentlemen, a health resort in what is now western Poland. Every day, its residents gather in the dining room to imbibe the hallucinogenic local liqueur, to obsess over money and status, and to discuss the great issues of the day: Will there be war? Monarchy or democracy? Do devils exist? Are women inherently inferior? Meanwhile, disturbing things are beginning to happen in the guesthouse and its surroundings. As stories of shocking events in the nearby highlands reach the men, a sense of dread builds.Someone – or something – seems to be watching them and attempting to infiltrate their world. Little does Mieczyslaw realize, as he attempts to unravel both the truths within himself and the mystery of the sinister forces beyond, that they have already chosen their next target. A century after the publication of The Magic Mountain, Olga Tokarczuk revisits Thomas Mann territory and lays claim to it, blending horror story, comedy, folklore and feminist parable with brilliant storytelling.