Have you ever sat down to consider the what-ifs of your book?
Trust me, you can make a story a lot more interesting if you simply think about and apply all the what-ifs. What if your barrister forgot the cream and grabbed the detergent instead? What if Jill didn't go out with Jack? Maybe everything doesn't end hunky-dory for your protagonist and the antagonist walks away with everything he wants.
For example... Have you ever thought about what The Sound of Music would have been like had they chose a German actress instead of Julie Andrews?
Okay, maybe that was a lousy example. But you get the point. Everything - absolutely everything - has what-ifs. The way it could have been or (for you as the writer) how it could be.
Think about the what-ifs. Sometimes they make your story more interesting. Sometimes they don't. Think outside of the box and imagine the possible as well as the probable.