I think this one is my absolute favorite of the series, if only for Orion. He's such an amusing guy. There is also something older about this book, as it's not simply a 'let's-save-the-world-adventure', and it's great to see some development in Artemis's character. It's been there previously, but it's rather stark here and of a more serious, adult nature. Which makes sense, seeing as how little Arty is now 15 (er...time gaps aside).