The Mirrored Shard by Caitlin Kittredge is the inconclusive finale of the Iron Codex trilogy.
Aoife Grayson had lived with her mother and brother, until her mother went crazy and her brother abandoned her. She had been enrolled in a boarding school and accelerating in her engineering classes. That was until puberty hit and she started to go crazy herself. She soon discovered her heritage and the key to her own personal power. Having been chased through the modern world of airships and even through the lands of the fae, she thought her life couldn't get any worse. But then the love of her life, Dean, died. Now she is determined to pass into the after life to bring him back to her. With a little help from friends and even a few enemies, she may just be able to fulfill her deepest wish.
There are a few complaints I have with the series that impaired my enjoyment of it. I never did get too attached to Dean's character, so the pairing with him and Aoife just seemed off. The final book is open-ended with the only conclusion being that Aoife has finally found it in her to take charge of her power and herself. That said, there are so many good things. I liked the steampunk world mixed with folk magic that Kittredge created. I enjoyed Aoife, Cal, Archie, and many other characters throughout the series. The interaction between most of the characters and the way events progress seemed natural to me. Overall, I enjoyed the series. I hope to see more works from Kittredge in the future.
Iron Codex series:
The Iron Thorn
The Nightmare Garden