The Hollow Kingdom Trilogy Series by Clare B. Dunkle

In nineteenth-century England, a powerful sorcerer and King of the Goblins chooses Kate, the elder of two orphan girls recently arrived at their ancestral home, Hallow Hill, to become his bride and queen...

For years, Emily has been living happily in the underground goblin kingdom. Now she is old enough to marry, but when her childhood friend, Seylin, proposes, she doesn't take him seriously.Devastated, Seylin leaves the kingdom, intent on finding his own people: the elves. Too late, Emily realizes what Seylin means to her and sets out in search of him... moreFor years, Emily has been living happily in the underground goblin kingdom. Now she is old enough to marry, but when her childhood friend, Seylin, proposes, she doesn't take him seriously.Devastated, Seylin leaves the kingdom, intent on finding his own people: the elves. Too late, Emily realizes what Seylin means to her and sets out in search of him. But as Emily and Seylin come closer to their goals, they bring two worlds onto a collision course, awakening hatred and prejudices that have slumbered for years. less

In the powerful final volume of the Hollow Kingdom trilogy, Miranda has waited her whole life to come home to the goblin kingdom, never imagining she'd feel so alone. Caught between two hostile races, she becomes their greatest reason for war--and only hope for a future.