The Second Sleep by Robert Harris
Robert Harris has written books set in ancient Rome (Pompeii), in 1938 (Munich), and in the near future (Conclave), so I was intrigued to see a medieval setting. Young priest Christopher Fairfax travels to a small town to bury their priest, but all is not as it seems, for Christopher or for the reader. Very hard to put down, with plenty of unpredictable plot twists. An antiquarian society is deemed heretical by the Church in this often dark, thought-provoking thriller.