So, how good are the AAMC CARS Question Packs, anyways?
The short answer is: they're great. They're by far the best CARS resource available.
The passages are exactly like what you'll see on the real MCAT. They cover the same subjects, they ask the same type of questions, and they're based on the same logic. In short, they're extremely representative.
The AAMC offers two CARS Question Packs—called Volume 1 and Volume 2—and between the two of them you get a total of 43 passages. It's worth doing every single one of them.
But there's a few other things you should know about them before you start.
The first thing is that Volume 1 is actually harder than the real MCAT. The difficulty is thrown off mostly by the first six passages, which are insane. They're the hardest passages you'll ever see. So don't lose hope if you get crushed by a few of them. (Picasso passage anyone?)
Thankfully, though, it does get better after that. The second half of Volume 1 is more average in terms of difficulty, and the difficulty of Volume 2 is spot on. Volume 2 is the best predictor of how well you'll score on the official AAMC Practice Exams and on the real MCAT.
But there is one thing that can throw that off: timing. Your scores on the Question Packs will only be predictive if you do the passages timed. If you take longer than 10 minutes per passage, you will likely score worse on the full length practice tests, because you'll struggle to get through everything in time.
So I suggest trying to get your timing under control as soon as you can.
Lastly, to clear up any confusion I just want to point out that the Question Packs are not the same thing as the Section Bank. The Section Bank only covers the sciences, not CARS. The Question Packs cover both the sciences and CARS, though the CARS Question Packs are much better than the science Question Packs. I don't know why the AAMC makes the names of these things so similar.
If you're wondering when you should start working on the Question Packs (and all the other AAMC material), check out my guide When and How to Use All the AAMC Material.