Sorry to put a dampener on things, but the way I'm reading these postings, it looks like the groundschool is being treated as a 'tick in the box'. I hope I'm wrong, and I don't wish to do anyone a disservice by suggesting that the theory isn't being taken seriously, but please, for your own sake, don't just view it as something you have to do in order to move on.
My advice would be to read your first Thom, self test yourself on it, start on the second Thom, top up your reading of the first, self test on the second, re- self test on the first (always looking for an improvement on your score), then start on the third Thom, etc, etc... Basically you're trying to bring your overall knowledge levels up, and then keep them there. And remember to go back to your books after you've got the exams under your belt; take them to the US with you, read a random chapter as a refresher when you're not flying. My old instructor taught me the saying on my signature, and I've never forgotten it. Good luck!