Some of the most memorable stories end told end with tears. Romeo and Juliet is designed to produce tears, and I became hysterical after I watched Terms of Endearment for the first time. Sadness certainly has its place in storytelling. But please, remember to lighten up sometimes. I should crack a smile, at the very least, during the course of your book...but I'd really like to laugh out loud.
Everybody Loves a Clown
Jokes have always had a way of bringing people together. Certain body muscle relax when you laugh, and sharing laughter with another will put you at ease. Ever sat in a crowded movie theater and heard everyone laugh along with you at the same joke? Laughter inspires camraderie. It's the basis for many friendships and even romantic relationships.
It's great stuff, and that's why you've got to make an attempt to add some humor somewhere to your book. What if you're writing a gritty drama, a serious tragedy, a tear-soaked epic?
To my way of thinking, that's when you need laughter the most.
Even tragedies need a little laughter, because nobody can be serious all the time. A joke here and there will alleviate tension. You cannot keep constant pressure on your readers, or they'll break. It's a pretty simple law of physics. If you place a bowling ball on top of a wicker basket and start to press down, that basket will buckle and break if you don't ever relieve the strain. But if you let up every once in a while and let that basket bounce back, you can go right back to applying pressure.
Take a similar approach with your readers. Put the screws to them. Drag them through emotions. Make them cry. But every so often, lighten up. Give them a joke, give them a laugh, give them a bit of a breather -- and then you can go right back to the tension. Your writing will be better for it, and your readers will be far, far more tolerant because of it.
So make 'em laugh...at least, every once in a while -- and make them keep reading.