A. A. Milne 
The Red House Mystery [EPUB ebook] 

The Red House Mystery is a ‘locked room’ whodunnit by A. A. Milne, published in 1922. It was Milne’s only mystery novel. A country house becomes a crime scene when the host’s brother is found murdered. Visiting a friend who’s staying at the house, Antony Gillingham fancies himself as an amateur sleuth. With his pal Bill (also a guest at the house), he sets out to solve the mystery. Chandler noted that The Red House Mystery seemed to have been in print in the US for about 16 years.