The Decagon House Murders (by Yukito Ayatsuji)

I've been recommending this to all the mystery fans I know, especially Agatha Christie fans! It's yet another Japanese locked room murder, which echoes and pays homage to And Then There Were None. It's perfect for fans of that novel. 

Anything else I want to say could maybe be spoilery so I won't.  But I love a mystery novel with a solid reveal at the end and this one definitely delivers.  (I'm still not over one I read recently where the solution was so convoluted that it required a complete stranger to coincidentally show up in the neighborhood and drop dead in a convenient location at the right time.)