A gem. Perfect. Deep and thoughtful and not a single wasted word.
I'm too old to have encountered this as a child, or even when my daughter was a child. I came to it without knowing anything about it except that it won the Newbery and everyone seemed to love it. So it unfolded for me the way books did when I was a child - every page a surprise. I was reading on Kindle in a version that contained an afterword by the author plus her Newbery acceptance speech, so even the fact that the book was about to end came as a surprise (it was at about the 85% mark). If you haven't read it, I recommend reading it that way.
It's a bit like 1984 for children, or maybe Fahrenheit 451 or The Dispossessed: a community that should be a utopia - everyone is happy, everyone gets along, everyone follows the rules, everyone has the perfect career and the perfect family life - but isn't, because of all the things people had to give up to achieve ripple-less equilibrium. There are no suggestions that any malevolent forces are at work; there are no bad guys, just a structure put in place generations ago. It's a cautionary tale, and it's a reminder of all the glorious things in life we might miss if we somehow found a way to take all the problematic bits out of human nature.