Steamborn by @Eric R Asher
YA/Teen Steampunk Fantasy
Steamborn, Book One
Jacob, a tinker's apprentice and sometime thief, has lived his entire life in the mountain city of Ancora, protected by the massive city walls. The towering barriers keep the Deadlands creatures at bay, but the monsters rise higher into the peaks every year. More and more they breach the defenses of the Lowlands while the Highlands rest easy.
A swarm overruns the walls and wreaks utter devastation on the Lowlands. Charles, the old tinker, suspects the attack may not be natural. With help from Jacob's closest friend, Alice, and Samuel, one of the city's elite spider knights, Jacob and Charles will uncover a terrible darkness at the heart of their city.