yeah definately worth buying them... why strain your brain trying to remember like a zillion rules off by heart when you can reference them in the exam... the more you flick through the regs the more it will stick in your head... If, however you are the thrifty type, buy AIPs and just borrow the rest... dont be an idiot by lessening your chances of success by not taking in all available resources.
Good luck with your exams!
P.s. Dont buy CAAPs just photocopy section 234 about the fuel recommendations.