 He had a fascination for the supernatural, first manifested in his early novel "Doctors Wear Scarlet", which features Balkan vampires (though they are practitioners of vampirism as a sexual deviation rather than an actual supernatural manifestation) and was cited by Karl Edward Wagner as one of the thirteen best supernatural novels.The Gothic themes became stronger in later works such as "The Roses of Picardie", "September Castle", parts of the "First-Born of Egypt" sequence, and the 1994 novella "The Islands of Sorrow".Although he acquired an enthusiastic and loyal following, he was never a top-seller in terms of the mass market.