Usually when fiction tries to be funny it comes of really badly. It is possible to do it well but it shouldn't be shoehorned in or be the focus of the story.
If they need to add some separate humor section in the book to keep the reader engaged it probably isn't a very good story.
But writing good fiction is a lot harder than people think, most people who try just don't get anywhere. I remember it being easy when i was a child but then i had my sister write half and i do not know if it was actually any good (i could ask here to send that).
Fiction written by me: