Dust

I have mixed feelings about this last book of the trilogy. I really enjoyed the comeback to the characters of the first book, like Juliette and Luke, because they were one of my favorites characters. And it was inspiring to see the revolution started in their Silo in search for answers and a better world.
But I felt a little bit unfulfilled with the lack of explanation of exactly what happened to the world. I don't know if I missed it at some point in the book, but it's still not completely clear to me why the silos were built and what was going on in other places of the planet. Maybe the author wanted it to remain a mystery, but I really hoped some more detailed explanation after reading the whole trilogy.
Another thing that bothered me is that when Juliette leads the people of her silo up to the surface, and then they walk towards the seed bunker and look at the dome of dust over the arrangement of silos, why didn't they try to reach the other silos? There were 50 silos over there and I didn't saw any hint that Juliette or the others were curious about them, or had the intention to free the other silos. My feeling is that there were too many questions unanswered in the story and that bothers me a little.
But overall it was a thrilling book to read with a pace that kept me going until the end.