how to study for AP Comp Gov

i just got the book Comparative Politics Today and it has 3 parts. The 1st part is the intro and talks about issues in comp politics and compares political systems. the 2nd part talks about political culture, policymaking, public policy, etc and the last part talks about the 7 countries(which is said to be most of the exam). So what i want to know is should i focus on the 1st two parts, or should i skip them and focus on the last part which is the seven countries part. You should also know that each part is extremely long and requires a lot of studying. Yet whats the point to waste my time on the 1st 2 if the exam is basically the last part.
By the way I’m not sure whether or not most of the exam is about the 7 countries i just heard it was.