Ellery Queen 
The Player on the Other Side [EPUB ebook] 

The game has begun… A playing card inscribed with the letter ’J’ appears in Robert York’s mail, and a day later he is dead. When another playing card shows up, this one for Emily York, all the police protection in New York can’t save her. Ellery Queen knows he is up against a brilliant, twisted killer, one who makes a game of death. But with no clue to his identity, Ellery is in a race against time to stop this remorseless vendetta. A brilliant detective story from a classic master of the genre.