The Opal Deception

This is the book in which the series grows up a little. Opal's first move strikes at the heart of the fairy police, costing Holly someone she deeply respects and leaving her framed for a crime she did not commit. Hunted by her own side, Holly turns to the only person clever enough to help, a human boy who no longer remembers her and is not inclined to trust a small woman with pointed ears who appears in his hotel room.

Winning back Artemis's memories, and his loyalty, is the emotional thread running beneath the chases, gadgets and explosions. Butler is as dependable as ever, the dwarf Mulch Diggums supplies rude comic relief, and Opal is a gloriously self-absorbed villain with a pair of devoted, rather dim pixie henchmen. Colfer keeps the plot moving at a sprint, and the loss early on gives the story more weight than the previous volumes.

Readers who were starting to tire of the formula usually find their interest revived here. Start with the first book, though; this one leans heavily on what came before. It leads directly into The Lost Colony. About 342 pages in the Disney-Hyperion paperback.