I do have a sequel to The Game Warden of Black Swamp planned. I'm currently working on a stand alone horror novel, then I'll move onto the Black Swamp sequel. That will probably be released early next year.
Now, for better news, I just released a new book TODAY, Tales from the Dark Distance. It's a short story collection that includes a Black Swamp novella! This novella will serve as a prequel to the next Game Warden novel, so it is important to the series. Please check it out if you are looking for a Black Swamp fix until the next volume comes out.