A Welsh hill farmer imports an expensive dog from the Black Forest of Germany. When this bites his son he promptly becomes a werewolf whenever there is a full moon. Sheep start getting mauled and part-eaten, then people, and . . .
Used availability for Guy N Smith's Werewolf by Moonlight
September 1974 : UK Paperback
July 2010 : USA, Australia, Canada, UK Kindle edition