Animorphs

Animorphs is a young adult science fiction book series written by K. A. Applegate. The series follows five teenagers who gain the ability to transform into any animal they touch. This power is given to them by a dying alien named Elfangor, who entrusts them with the mission of fighting the Yeerks, a parasitic alien race that infiltrates and controls other species by entering their brains. The five human teenagers are Jake, Rachel, Tobias, Cassie, and Marco. Later, a sixth member, a Free-Trading alien named Ax, joins their group.

The Animorphs operate in secrecy, using their morphing abilities to gather intelligence and carry out missions against the Yeerk invaders. They are often forced to make difficult moral choices, dealing with the psychological toll of war and the constant threat of discovery. The series explores themes of morality, the nature of good and evil, the consequences of war, and the loss of innocence. The books are known for their relatively mature handling of war-time themes for a young adult audience.

The Animorphs series ran for 64 books, published between 1996 and 2001. It was a commercial success, selling millions of copies worldwide and spawning a television series, a video game, and various merchandise. The series is divided into several story arcs, with the main narrative focusing on the ongoing struggle against the Yeerk empire.