Having read this once at around the age of eleven and again, well, yesterday, this feels like a completely different book. When you're eleven, I think you're more prone to clue into the personal aspects of the story: no, this isn't fair to Jonas, because that's how I in my eleven year old brain am feeling right now. Reading this again at more than twice that age, the bigger picture is more overtly what drives the story: how can people live in a system like this, and I see some of these same flaws in the system that surrounds me. 
 I guess what I'm saying is, if you read this as required reading as a kid, like I did, it's definitely worth a second pass, for lots of reasons. 
 As a side note: I love Lowry for her ability to talk up, not down, to younger audiences while at the same time including enough in the story (in the way not just of details or dialogue but also overarching theme and development) that it becomes a completely different book for older readers.