Open book tests are deceptive. You'd think they would be easier because you have all your materials right there. However, if you don't know the stuff cold and use your outlines for anything more than the occasional reference, then you will not finish the exam and probably do very poorly.
Truer words were never spoken. I study for open-book exams in the exact same way as I study for closed-book exams. It is simply unrealistic to believe that you will have all of the time in the world to consult your materials, read and take notes on the question(s), sketch a rough skeletal outline, and then write the actual answer(s).
Howver, it is for this exact same reason that there is a bright side to open-book exams: people typically understimate them, meaning that if you yourself don't do so, you can, and probably will, perform better than they.
I never perform well on my exams. I'm stuck babysitting my BB Sternchat.com. Those fuckers don't care about me or my needs at all. I have to start all over now.