Zuna is an interesting super villain-- he has so much money and power that he seems unstoppable, but has certain weaknesses. I loved that Strike had no intention of trusting him, but was sucked in by his desire to continue with his sport. The fact that the players will take horrific chances to stay in the Ultrabot suits has direct parallels to football players continuing to suit up despite the threat of concussions and traumatic brain injury.
The best part about this is, of course, the Miners and the variety of characters on the team. My own favorite was Torch's sister,who shows up wanting to help the team in any capacity, and who ends up being a formidable player in her own right, earning the nickname "Nitro". It made me very happy that the Ultraball players were about equally male and female, and there wasn't much discussion that this was anything unusal. Is it going to take the destruction of the entire Earth, a Moon colony, and robotic suits before we get gender parity in sports?
Ultraball is such an unusual mix of elements that it's hard to find books like it. Readers who go back and forth between Tim Green and Mike Lupica and then Jason Fry, Joshua Levy, and D.J. MacHale will wish that they were able to take their own game into space.