Four children looking forward to an ordinary summer enjoy a series of fantastic adventures by double-wishing on an ancient coin.

Presents thought-provoking answers to questions children might have about the nature of time, space, the universe, and mankind's place in it.

Four children find a magic way to go back into the time of Ivanhoe and Robin Hood.

America's most celebrated astrophysicist invites young readers to explore the mysteries of the universe.

"An enormous snow-covered mountain has appeared in the Pacific Ocean. No one knows when exactly it showed up, precisely how big it might be, or how to explain its existence. When Harold Tunmore, a scientist of mysterious phenomena, is contacted by a shadowy organization to help investigate, he has no idea what he is getting into as he and his team set out for the mountain. The higher Harold's team ascends, the less things make sense. Time moves differently,...

In this conclusion of the tale begun in "Over Sea, Under Stone," Will Stanton, the Welsh boy Bran, and the Drew children try to locate the crystal sword that alone can vanquish the strong forces of Dark.

Budding scientist Lucy builds a rocket ship and accidentally sends her beloved dog, Laika, into space.