As my teachers in high school used to say- the person marking your exam probably is doing so at 11pm in a dimly lit room with a lamp and a cup of coffee in one hand. Don't make their life any harder than it needs to be. Just show that you are able to articulate your point and tick off the required knowledge quickly and cleanly.
ps. As others mentioned, you can ask for extra books if it's for the essay. Not recommended for short answer since it gets messy. The lines they provide should be more than enough to articulate a response which can earn full marks for most people.