I read it recently, and the exact same thing happened to me as to you: it was recommended to me, I didn't have high expectations, and it blew my mind. The way Zevin describes Sam and Sadie's friendship, with all its ups and downs, felt so real to me that it sometimes hurt. And the video game thing is just the backdrop, but at the same time, it's the language through which they communicate. I was fascinated by that part, how something so intimate and complex can be created from something many see as a simple distraction.