<p>Yes, GridWorld is very important since you’re sure to be tested on it (make sure to familiarize yourself with the AP Quick Reference they’ll give you for the exam). Also, make sure you have a solid knowledge of the standard data structures tested (simple data types, classes, lists, and arrays) and how they work as well as sorting and searching methods.</p>
<p>In terms of books, I just used a Barron’s from 2010. Although it does contain some superfluous material, it contains pretty much everything you need to know.</p>