Brief Synopsis
The books are about a young brother and sister, Zak and Tash, who travel the galaxy with their mysterious Uncle Hoole. Tash and Zak are orphans; their parents were on their homeworld of Alderaan when it was destroyed by the Death Star. Tash is fascinated with the Jedi, while Zak is interested in machines and technology.
The first six books form an arc. The protagonists discover pieces of a large Imperial experiment in biological weapons, codenamed Project Starscream. The first five books deal with the heroes discovering the various components of Project Starscream, each dangerous in its own right The sixth book deals with their discovery of the final goal of the experiments: creating a prototype organism, simply named "Weapon".
The next six books lacked a central arc. The protagonists, now wanted fugitives, simply travel from planet to planet attempting to avoid Imperial authorities. Each book told a story of the main characters stumbling onto some danger and the resulting adventure.
Read more about this topic: Galaxy Of Fear