Dragonbreath: No Such Thing As Ghosts by Ursula Vernon
It's Halloween, Danny and his best friend Wendell are going trick or treating. Wendell' mom, who can't sew and loves educational things, made his costume. Danny isn't happy to find out Christiana, a girl from their class will be going with them. When Danny's dad their chaperon has his back turned Big Eddy challenges the three to go into a haunted house.
Once inside all the exits are locked and they can't get out. Thanks to previous adventures Danny and Wendell need little convincing about the existence of ghosts. Christiana refuses to believe in ghosts without any evidence. To leave the house the three must first explore it. In the process they run into a very creepy clown.
This is the fifth Dragonbreath book. Danny and Wendell still have the same wonderful friendship chemistry. Christiana's straightforward practical sensibilities play off of the two very well especially Wendell. I love this series and always look forward to the next adventure. A great recommendation for Wimpy Kid fans.