Don't just read your own writing when you work on a book. Surround yourself with great books that inspire you, teach you quality prose, and show you techniques you may have never thought of before. In the vein of writing comedy, here's a list of books that make me laugh and that I think EVERY writer should read if they want their readers to laugh.
First, Eric Idle's THE ROAD TO MARS. It's hard to find, but I bet if enough people pester the publisher, it'll show up in an ebook format. It's hilarious. The storyline is engaging. And it's one of the best essays I've ever read, which is funny because it's just a novel!
Next, pick up anything Gail Carriger has written. That's comedy. Seriously, go do it now before you finish reading this. Go. Do it.
Finally, read The Dresden Files series by Jim Butcher. It's not filled with humor the way the rest of my recommendations are, but they have comedy woven in so smoothly that any writer who wants to write serious fiction with a hint of humor should read this series. It'll give great ideas on how to keep the humor subtle without interrupting the flow of the narrative.
But if you don't like to laugh, then I will light a candle for your soul. And weep for the future of mankind. Because, let's face it, laughter is one of the greatest joys in life.