Hi
I'm just about to do my aircraft general exam but using the Jeremy Pratt book, not that it makes much difference as I've used a combination of both Thom and Pratt with my other exams. You only need to learn the "aircraft general and principles of flight" section of the book. There is another exam covering "flight performance and planning" so no need to learn that yet until the time comes (probably after this one). There is a slight overlap between aircraft general and meteorology so hopefully you've passed met already? You might get a bit stumped on some of the questions if you haven't. The confuser is a total god send so get a copy if you haven't already (however still out of print I think but some on ebay!).
Good luck with your exam!