Well, it can't be too complicated if I was able to have an even superficial grasp of it when I was in middle school back when I first read about it. However, some aspects of it when explored as thought experiments are immensely counterintuitive. Further, the implications it has for order of events and how faster than light communication can ultimately result in breaks in causality (as some people have supposedly put forth) are what are most interesting and most complicated to grasp. And that's what I plan on going over next assuming my fickle nature does not take hold of me tomorrow.
I'm trying to put it in words that are relatively easy to follow, as well, as the intention is to teach for those who may not have any particular education in even so much as physics. Or at least as simply as I reasonbly can without doing any serious planning. But, my ADHD makes my train of thought drift, so I'm probably getting off track.
If anyone wants to add something, feel more than free to jump right in. Add, clarify, discuss, elaborate, take over, whatevah!