I'm not sure specifically as I haven't read it. It could be about some hounds named Bumpus during Christmas time, perhaps they have an adventure or some heart - warming experiences related to the Christmas season.
The 'bumpus hounds christmas story' might be a story that focuses on the Bumpus hounds and how they interact with the Christmas festivities. Maybe they help their owners prepare for Christmas, or they get into some sort of Christmas - themed trouble. Without reading it, it's hard to say for sure.