The Santa Klaus Murder

From Crimereads.com: "Originally published in 1936, Mavis Doriel Hay’s The Santa Klaus Murder is generally regarded as the blueprint for the zillions (at a rough estimate) of English manor house Yuletide murder mysteries to follow. It has all the elements—a family gathering at the ancestral home; a universally disliked and quickly dispatched family patriarch; multiple suspects hiding multiple secrets; and a dogged investigator trying to make sense of it all. But what really makes this Golden Age mystery unique is the author’s unusual choice to include multiple perspectives as each suspect writes his or her statement. In this very cleverly plotted mystery (which includes that lovely old-fashioned reader’s aid, the detailed floor plan), a guest dressed as Santa Claus (or Klaus, if you prefer) finds family patriarch Sir Osmond Melbury on Christmas Day with a bullet in his head. As usual there is no dearth of suspects, but their motivations are a bit more difficult to winkle out."