Brian's Birthday Bloodbath by Brian G. Berry
It was Brian's twelfth birthday today. He was looking forward to having a night over with his friends. Jessica, his lifelong crush, was coming over to babysit the three of them. It was going to be a night of fun; watching horror movies, playing video games, everything he wanted to do. But, there was a Clown on the loose; a deadly clown freshly escaped from the Shady Sands Institute, and he was hungry. Leaving behind a trail of slaughter and half-devoured bodies, Bones the Clown cuts a path to the town of Oak Falls where he smells something he likes, and it isn't birthday cake. Brian's Birthday Bloodbath is the fourth title in the Slasherback series; and the most extreme.