Animorphs - The Android
When Marco runs into his old friend Erek he doesn't think too much of it. He's got a couple of more important things to do. Like helping to save the world. But then Marco finds out Erek's been hanging with some of the kids at The Sharing. And he starts to think that something just a little weird is going on.

So Marco, Jake, and Ax decide to morph and check old Erek out. Just to see if he's been infested with a Yeerk. The good news is that Erek's not a human-Controller. The bad news is that Erek's not even human...
Science fiction, Fantasy fiction, Juvenile fiction, Fiction, Fantasy
Katherine Applegate
Katherine Alice Applegate is an American writer, best known as the author of the Animorphs, Remnants, Everworld and other book series. She won the 2013 Newbery Medal for her children's novel The One and Only Ivan. Applegate's most popular books are science fiction, fantasy, and adventure novels. She won the Best New Children's Book Series Award in 1997 in Publishers Weekly. Her book Home of the Brave has won two awards. - [wikipedia](https://en.wikipedia.org/wiki/Katherine_Applegate)