The Strangers (Animorphs #7)
Okay. Rachel and the other Animorphs have finally found the new entrance to the Yeerk pool. They've even figured out a way to sneak in. The infamous roach morph. But they didn't count on roaches being a Taxxon delicacy. This time escape doesn't look so good.
And then everything stops. Everything, The Feasting Taxxon, the human-controllers, the Hork-Bajir, Time, Now Rachel, Cassie, Marco, Jake, Tobias, and Ax are in for their wildest trip ever. They're going to get the chance to decide whether they want to stay on Earth and fight the Yeerks. Or go to another planet. And the guy giving them the choice says he can save them. Now all they have to do is make the choice...