The Endless Sky (Paperback) (ISBN-13: 9781926946061)

Oh God, oh God, oh God, Mud's leading the team this time. Duck.
Stepping into his parent's boots, Mud Madison (please stop calling him 'Newt') is still breaking in his new Insertion Team. Everything is going smoothly enough, until the answer to a long-standing mystery forces them to deal with a mulit-versal incursion that no one was prepared to accept as even possible.
It's five against the impossible. Luckily they have each other. And gravity packs. And blasters. And grenades.