So sorry this review was so long in coming. I actually read this book in only a few days. Since it's been a month, my review will be a little generalized because of the passage of time. However, the most important thing I thought while reading this was this:
This is reminiscent of "Ender's Game" while being completely unique!
Yeah, I'll try to explain that thought. The theme of Sleepless is very similar to Ender's Game. Humanity has spread to several planets, and the current civilization has been shaped by a previous war. The military has spent a long time trying to ensure victory in case of another attack by the Splicers. Part of that process means testing children to find the limits of their intelligence and abilities. Aidan is the one the leaders have set their hopes on.
Here's where Twiss makes his story uniquely his own. Primes.
Primes are not human. They are genetically engineered to have special abilities like speed, strength, the ability to change their density, engineering (mechs), and puzzler mode. (You'll just have to read to get a full grasp on what I'm talking about here.
Twiss does a great job teaching you about his world without huge info dumps. He throws the reader in and lets you figure it out with little hints here and there. When things get complicated, he let's it be something new the cadets are learning about themselves so the reader doesn't get lost.
I LOVED the twist with the SIMS. And the secret behind Aidan's birth. :) I won't give away any spoilers here! However, I'll say this was a fun, fast, energetic and at times edge of your seat ride. I'm looking forward to seeing where the story goes in book two of the series.