Engine No. 9. Clockwork Empire

A clockwork former Union soldier turned vigilante and a secret agent are all that stands between the United States, weakened by Civil War, and a power hungry empire determined to cross the Rocky Mountains and take it all. Good thing they're both armed and dangerous... Jeremy Smith lost his arm when it was blown off by a scatterbomb in the battle at Antietam. Now he's known as Ryder, and follows the telegrams across the West, sent blindly to him from desperate people hoping to find justice, or just someone who cares enough to help.
Ryder's got an iron clockwork arm, given to him during the war by the brilliant Mexican doctor Ferdinand Santos. Santos has built Mexico into a world power, controlling territory from Alaska all the way to South America. Lucy Monroe is descended from an American president. She takes her heritage and her job as a secret agent in the Presidential Auxiliary Service very seriously. Lucy and her team are sent to Sierra Blanca, Texas with one mission: to make sure that Santos's empire-building stops at the Rocky Mountains.
And no one is going to get in her way. Ryder ends up in Sierra Blanca after he receives a mysterious telegram asking for his help. He has no idea who sent it, but somehow he lands right in the middle of a territorial tug-of-war between Santos and the U. S., which is still recovering from the war, just like Ryder is. Lucy doesn't trust him, and he doesn't trust her-or her crew of knife-wielding, gun-toting fake waitresses. His old commanding officer arrives in Sierra Blanca, now working for Santos, and dead bodies start piling up.
The tensions are high and danger is always nearby, so why is it all he can think of is finding out where Lucy hides all those nifty weapons under her ever-changing disguises?He's iron-arm deep in clockwork bad guys, murderous waitresses, an irresistible, cantankerous spy, English Navaho airship troopers, and a whole lot of scatterbombs. And he and Lucy are standing right in the center. Good thing they're both armed and dangerous.