Diane Duane

Thirteen-year-old Nita, tormented by a gang of bullies because she won't fight back, finds the help she needs in a library book on wizardry which guides her into another dimension.

Nita and Kit return from their wizardly holiday, looking forward to getting back to their everyday routine. But there's trouble brewing. A strange darkness of the mind and heart is about to befall the older wizards of the world, stealing away their power. Soon, the young wizards of Earth and many other planets find themselves forced to defend wizards and nonwizards alike against an invasion of a kind they've never imagined. But mere defense won't...

Coming to the aid of a wounded whale, Kit and Nita are plunged into deep wizardry. The whale is a wizard, and she enlists Kit and Nita in battle against the sinister Lone Power. Becoming whales themselves, Nita and Kit join in an ancient ritual performed by whales, dolphins, and a single fearsome shark. But which poses more of a danger: the Lone Power, or ed'Rashtekaresket, the enormous shark as old as the sea?

One hundred years ago, four crewmembers of the U.S.S EnterpriseTM crossed the dimensional barrier and found a mirror image of their own universe, populated by nightmare duplicates of their shipmates. Barely able to escape with their lives, they returned, thankful that the accident which had brought them there could not be duplicated, or so they thought. But now the scientists of that empire have found a doorway into our universe. Their plan is to...