Wha? Serious Humor sounds like an oxymoron. Well, it is, but it’s also a legitimate technique that I love to use.
Serious humor is mostly situational. A character is engaging in activities that are not humorous, but something occurs to make them humorous, or the nature of the scene makes it funny. I used this type of humor a lot in How to Win Friends and Influence Magicians. You get all the laughs of a joke without ruining the serious messages of your book.
Example:‘“Really?” I scolded the nearest building, showing it my most fierce expression of reproach. “Is this how you’re going to do it?” The building tried to pretend it didn’t hear me. I turned to a building on the other side that I know was in on the whole thing too. “Are you serious?” I demanded of the building. “Are you honestly going to set up some hocus-pocus barrier to keep me in like a trapped rat?” The building looked belligerent, knowing it was guilty. But it didn’t apologize. So I yelled at it for a while, though it didn’t help me get out.’
Everyone has yelled an inanimate objects. The character is serious and angry, but the situation is funny. Serious humor!
Another example would be a group of characters following another character in secret. The purpose is serious and the characters are serious about it, but you can make it really funny as they try not to get caught and have to react to the movements of the one they are following.
Face it, life is hilarious. If it doesn’t make you laugh, it makes you crazy. So laugh! It costs less than institutional care.