Bit of a slog at the beginning, which is likely due to my own problems with the story structure. It begins as exchanged letters between two teenage girls, seemingly Victorian era. I can see how this would be attractive to collaborating authors, and fans of letter writing everywhere, but I always have trouble wrapping my head around that kind of narrative. Once it gets going, it gets a little better. The authors do a decent jobs of within-letter asides that help explain things, but it's clearly best if one already knows something about Victorian society, structure and constraints. In the afterword, the authors explained how they didn't communicate directly about the plot until three or four letters within the ending of the novel, which is amazing given the relative coherence of the book.Being generous, I rounded upward; I think this is a 2 and a half star book for me, but if you like the narrative structure, undoubtedly it will rate higher.