What does it mean for a novel to have an inherently humorous premise?

Lately I've been getting a little fed up with all the very serious novels in the world. I open up a book, and it's just...heavy. Even when it's a love story, there's just so much drama and angst. The heaviness permeates the whole book. It sinks into the writing itself. The sentences are long and lugubrious, and they dwell heavily upon the landscape and …