The characters are fun as well. M struggles with her memory loss, which makes her trust Evel long enough to discover that he's not all bad, even though he's a Ronin. Her friends Chloe, Emma and Jenny are a fun mix of typical tween girls and spies with ninja-like abilities. Villains Cal and his mother Mrs. Watts show up... but are they really villains?
The difficulty in determining which side is good and which side is evil gave me some pause, but readers of Artemis Fowl will enjoy the ambiguity, and the excitement of not really knowing what the next move should be, and whether or not M is one of the good guys or one of the bad guys.
This is the final book in the series, but readers who want more will be well served by picking up Walden's H.I.V.E. series, Jinks' Evil Genius or Gibbs Spy School series. You never know when your middle school art teacher might crack, and there are lots of good spy tips to learn from these books, just in case you need them!