The Thirteenth Tale by Diane Setterfield.  The reclusive author Vida Winter has spent the last six decades creating alternative lives for herself.  But now, as she succumbs to terminal illness, she summons Margaret Lea, an amateur biographer, to tell her last, true story.  This is a fabulous gothic mystery, complete with ghosts, governesses, and a decrepit manor house, and it's a fantastically rich story to boot!
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