I started this book on the ferry ride to Macao, which was unexpectedly appropriate. Serendipitous settings aside, this is probably the weakest book so far in the series. The first 3/4 of the book are written with the same air of mysteriousness than Kitty has spent the previous books making fun of. When you finally get to the meat, there are only a few pages between it and the conclusion. And the ending is a cliff hanger.
I would have rated it lower if I had entered it right after reading it, but I've read enough of the sequels now to know that most of this book is necessary setup for future, better stories. So, while initially less enjoyable than it's predecessors, there is eventually a good payoff.