Engines of Alchemancy - The Alchemancer, #1

Elemental magic consumes the world and only a sorcerer's apprentice who knows nothing about magic can stop it. The Alchemancer series begins. Chaos erupts in the Barony of Fallmere when a surprise elemental attack destroys Norwynne Keep. Aaron Shepherd and Shanna Bonnerman survive, but Shanna is soon lost in the fallout of the keep's destruction while Aaron is forced to flee for his life. Unbeknownst to Aaron, Shanna becomes a captive of the enemy who destroyed their home.
This enemy, a savant who claims to follow the path of science, speaks of ancient, infernal devices and a quest to reclaim the greatest of them all. Certain the savant means to kill her, Shanna is instead surprised when she finds herself embarking upon the adventure of a lifetime. Meanwhile, only the worst of nightmares awaits Aaron. Pursued by dwarven raiders, mad sorcerers, and a host of demons who will not stop until he is dead, the only thing keeping him alive is his own wits and an eslar mercenary whose reputation as a killer might make him the worst threat of all. Though Aaron and Shanna travel different paths, their purposes align when they each learn of a mysterious device known as the Fifth Element.
Shanna sees it as the final piece of the puzzle that is her destiny. To Aaron's logical mind, it is an impossible ambiguity. Whatever the answer, the Fifth Element draws them back together and into a final confrontation where science and sorcery will collide.