I'll nominate The Thirteenth Tale
by Diane Setterfield, although I suppose some might not consider it a mystery (it's certainly not classic genre mystery)...
Sometimes, when you open the door to the past, what you confront is your destiny.
Reclusive author Vida Winter, famous for her collection of twelve enchanting stories, has spent the past six decades penning a series of alternate lives for herself. Now old and ailing, she is ready to reveal the truth about her extraordinary existence and the violent and tragic past she has kept secret for so long. Calling on Margaret Lea, a young biographer troubled by her own painful history, Vida disinters the life she meant to bury for good. Margaret is mesmerized by the author's tale of gothic strangeness -- featuring the beautiful and willful Isabelle, the feral twins Adeline and Emmeline, a ghost, a governess,a topiary garden and a devastating fire. Together, Margaret and Vida confront the ghosts that have haunted them while becoming, finally, transformed by the truth themselves.