The Emperor's Bones

From fantasticfiction.co.uk:
The stunning new historical epic blockbuster from the author of THE PALACE OF HEAVENLY PLEASURE. Beautiful, headstrong and unconventional, Catherine Cabot is twenty years old when she arrives in China. Against an uneasy political background a bittersweet, triangular love affair develops between Catherine and Edmund and George Airton. And all the while, she is trying to uncover the truth of her past, unaware of the danger this might pose to her. Who is Henry Manners, the mysterious man who once wrote to her mother, and who she knows now lives in China? Returning to China alongside Catherine is Yu-Fu-kuei, a Chinese revolutionary working as a Communist spy. She and Catherine met when they were at Oxford immediately after the Great War, and the friendship is deep and permanent. As the Japanese mass themselves on the borders, waiting for an excuse to invade, Catherine, ignorant of a history steeped in hatred, unwittingly becomes the perfect tool to settle the scores of two men who will stop at nothing to wreak their revenge. And Yu-Fu-kuei discovers that love might be the strongest weapon that any warrior has.