In my opinion, it's one of the more interesting books in the series. The plot strays from the rest of the books somewhat but in good ways (gives a lot of nice twists to the story which make you want to keep reading). The plot thickens and the characters continue to develop, including Saint Dane, who is becoming more cunning and evil.
I have always been a fan of the books and this one in particular is a fave solely because of a few twists that you will have to read to find out (one sad and the others adventurous. I obviously don't want to tell you what they are but you will know what I'm talking about if/when you read it). I was happy that Mark and Courtney got to play larger roles in the book and glad Spader made a come back (he is hands down one of my favorite characters). I was very frustrated that Mark and Courtney didn't think to use the rings to communicate with each other acolytes over certain issues that arise in the book, since they have done it before... so I was slightly confused on why Mark and Courtney made the choices they did when they said they no choice... but other than that little hole, the book was a great read.
Finishing this book made me eager to pick up the next one, which is something I haven't totally felt with the other books. D.J. MacHale continues to give Bobby (and the readers) twists that then never see coming and that are filled with plenty of mystery and adventure. I still am in love with the writing style (going back and forth between Bobby on his adventures in his journals and Mark and Courtney's lives) and can not wait to see what happens in the next book as well as what other territories have in store (the cats with human slaves thing threw me for a loop this time) :) Hobey-Ho let's go!