I stumbled across The Decagon House Murders, and after reading the summary, it reminded me of Agatha Christie's And Then There Were None. It seems that this book is definitely based on the aforementioned novel, and has a lot of great critique.
I'm thinking this book would be an interesting pick for Country House Mystery. And maybe Locked Room Mystery as well?
I read And Then There Were None for the locked room square last year. So I figure that a book based on in would also count.