That's a tough job for anyone, much less a hapless teenage boy.

Thus begins Superior Saturday, the sixth part of The Keys to the Kingdom by Garth Nix. Arthur has overcome the other days of the week--Monday through Friday--the failed Trustees of the Architect.

Although Arthur (the Rightful Heir to the Architect) now holds five of the Keys and has liberated five parts of the Will, Superior Saturday and Lord Sunday between them are still more powerful.

Arthur and Suzy seek out help, ingeniously bypassing the many ways Saturday has closed her tower, only to find that the sixth part of the Will's hiding place represents a whole new challenge.

Meanwhile, back on Earth, Arthur's friend Leaf struggles to get a huge number of sleepwalkers to safety, including her beloved Aunt Mango.

Nix ups the ante in this volume. Arthur faces entirely new threats, some of which he's never suspected. Despite all, however, he is a terrific young hero, determined to prevail no matter how bad the odds.

Suzy Turquoise Blue provides a fitting foil for Arthur, her saucy wit balancing Arthur's serious intensity. A millennia-long Denizen of the House, she knows the ins and outs better than Arthur does, but lacks the drive he has to overcome obstacles and beat the villainous Trustees. Their back-and-forth banter is about as lighthearted as the series gets in this volume, where the stakes could not be higher.

Saturday, though little seen, proves an interesting new opponent for Arthur. She has had a much larger role behind the scenes than anyone has realized--but things are not as they appear and some important truths are yet to be revealed.

Fans of top-notch YA fantasy will love this series. Nix is a masterful storyteller, with an imagination not locked into classic (and shopworn) tropes; as with D.M. Cornish (Monster-Blood Tattoo ) and Holly Black (Spiderwick), Nix fearlessly reinvents the YA genre in his own mold. He provides readers with high adventure, thrills, a handful of frights and a pair of resourceful heroes in the battle against darkness and ruination. What more could you want?

Strongly recommended.