I took AP Human Geography as a freshman, in 2010. It was my very first AP class and AP exam, and all my prep included was reading an OLD Barron's book. That thing seemed archaic, pre-2000 maybe even. I made a 4, and that was before they removed the -1/4 rule. My program was terrible, and I practically self-studied. I was the only student in my graduating class to pass the exam, and 60+ students took the exam after the year-long course. Sad, ain't it?
Read a prep book, and you'll be fine.