The Wonder Engine (Clocktaur War #2) by T. Kingfisher

In the sequel to CLOCKWORK BOYS, Slate, Brenner, Caliban and Learned Edmund have arrived in Anuket City, the source of the mysterious Clockwork Boys. They even managed to build some trust in each other’s skills. That trust is built on quicksand as the risks continue to escalate. But the secrets they're keeping could well destroy them, before the city even gets the chance…

Old foes and consequences of past decisions lurk in the shadows. Every team member’s skills are required to succeed--even more so if they hope to survive.

The Wonder Engine never lets us forget our funny, broken group even as the action propels our heroes to new highs and lows. It shows that making the most of the rest of your life can be rewarding--no matter how many mechanical abominations you need to destroy to get there.