Gilded Lies. The Immortal Grimm Brothers' Guide to Sociopathic Princesses, #5

Not all Grimm Brothers' tales are famous, a fact Larkin Gregory knows all too well considering her little kingdom of Liliental is all but forgotten. When her siblings disappear one by one, the victims of a sinister plot, Larkin sets out to find them at all costs. With the help of an amnesiac price, a set of journals, a mysterious trunk, and an inner monster she never knew she had, Larkin hops a plane to Germany determined to save her siblings from the clutches of evil-even if she can't remember anything from her supposed former life in a fairy tale kingdom. From the very beginning, things go all wrong.
Kidnappings, mythical magic spells, wolf shifters, evil half-siblings, and all manner of nasty creatures threaten Larkin's survival, but she refuses to give up her search until her sisters and brother are safe with her again. As her memories of a life long ago resurface, Larkin must learn to navigate both the past and the present to ensure she has a future.