Not the strongest of the series but thematically, I think it fits very well as an end to the series. Wish we'd gotten a more definitive end to the story of the Quagmires and Fiona but that's okay, the book leaves the ending nicely in the middle with some things solved while others are not. Did not care for the new characters introduced and the plot of the island though. 

All in all, I do like this series. It picks up steam as soon as it starts deviating from the formula but the individual stories are not always as interesting as the overall mystery. Love how this slowly builds up very complicated themes for a younger audience and the writing style is surreal, funny and phenomenal. Would've loved this if I were younger but I'm glad I got to enjoy it now.