I can't let the opportunity go by without nominating one of my favourite authors: Barbara Vine - A Dark-Adapted Eye
In the Edgar Award–winning classic, a niece investigates the shocking secrets that condemned her once proud family
Faith Severn has never understood why the willful matriarch of her high-society family, aunt Vera Hillyard, snapped and murdered her own beloved sister. But long after Vera is condemned to hang, a journalist’s startling discoveries allow Faith to perceive her family’s story in a new light.
Set in post–World War II Britain, A Dark-Adapted Eye is both a gripping mystery and a harrowing psychological portrait of a complex woman at the head of a troubled family.
Amazon (US): LINK
B&N (US): LINK
It's also available in Australia and UK.
Additionally, it's available all over the place in Overdrive so hopefully you can find a copy somewhere.