An Unsuitable Heir by KJ Charles
While I agree with Caz that the romance itself is a bit underdeveloped, I loved this story! Pen was such an interesting character, I loved how Charles wrote him, and how that part of the story developed. And the mystery was finally solved! The entire series was really well done, the twists and turns of the overarching story were captivating, and I was more than satisfied by the ending to the story.