Have you noticed the trend in the modern dystopian trilogies? I'm talking about the likes of The Hunger Games, Divergent, Matched, Delirium.
Book 1 is all about the world, the interesting setting, and how it's dusfunctional.
Book 2 sets up the rebellion, sometimes with the heroine reluctant to join.
Book 3 is the war.
I love reading about new ideas, so the first book in a dystopian series is always a delight. What follows is just a rehash of World War Two set in that imaginary world. You get sewers, home-made explosives, capture and torture. You get the civilians and children involved. You eventually claim the bitter-sweet victory.
I can't help wondering whether there is an improved formula somewhere.