The thing that absolutely kills most synopses is too much information. The author cannot keep the entire book out of his/her head. So how do you fix that?
You scrub your brain of the crap...after you find your direction.
When people ask you what your book is about, do you stutter and stammer and then attempt to tell the entire novel in the span of two hours? *clucks tongue* The light of "that's interesting" dims after about the second sentence. When the average person asks you what you're writing, they're looking for something short and sweet so they can go, "Wow, you're so cool and exciting. When I grow up, I want to be you."
So far, I haven't gotten that yet.
So you want to give them your Bullet, the one sentence that describes the book.
For Fall of Sky City, the bullet is this:
Nix thinks she’s captured the ultimate prize, Synn. But is she strong enough to control him?
Now, find (3) Plot Points using your Bullet as your compass. Ignore the minutia. Pay attention to what that line of thought hit.
PP1. Getting captured by Nix and tortured.
PP2. Escaping Nix and trying to survive on the outside.
PP3. Striking Sky City.
Now, let's try to do the same thing with the character plot. Find the character plot Bullet.
After being captured, beaten and broken by Nix, Synn discovers there's more to life than surviving.
Find (3) Character Plot Points using your Character Bullet as your compass.
CP1. He sees his father murdered in front of him as Synn is Marked.
CP2. He discovers that he's been compulsed by Nix, so that after he leaves, there's something inside of him pulling him back.
CP3. He sees her Knight destroy an entire city and kill their lethara trying to get to him.
All right! These sound pretty strong...and they don't make a lot of sense. Right? How in the world did we go from escaping from Nix to attacking Sky City?