Animorphs

"Animorphs" is a science fiction book series by K.A. Applegate about a group of teenagers who gain the ability to morph into any animal they touch, through the help of a dying alien called Andalite. Their newfound power is used to secretly fight a covert war against invading parasitic aliens called Yeerks, who control humans by invading their brains. The series explores themes of identity, morality, and sacrifice as the teens balance their normal lives with the dangerous burden of resistance. The books combine action, moral dilemmas, and complex character development, appealing to young readers and adults alike.