Review book for AP Micro/Macro?

I want to get the Princeton review, but the new one is too expensive… will a 2015 version of a review book still be okay? I don’t think they redesigned the exam recently. The 2015 one is $1.25 while the 2018 is $15, and I’m wondering if there’s a huge difference between them.

I have the 2018 edition, I think that I would invest in 2015 one, from what I know Princeton review books do not really change that much from one year to the next. I would go for 2016 or 2017 edition, it’s more recent and it is $1.25 for 2016 and $11 for 2017 from what I’m checking out on Amazon.