These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
It Was His Sled: The fact that Ember is an Underground City is not found out until the end of the first book, but good luck finding someone who treats that like a spoiler (Hell, it even says this on the main page!).
Paranoia Fuel: One doesn't have to be a rocket scientist to figure out that the situation in The Prophet of Yonwood (the U.S. battling a terrorist nation that threatens total war) is a natural progression from what the world is going through today.