The Familiar
Imagine if one day you went to sleep, and the next day you awoke in a future where your worst enemies had invaded your home land -- meaning you had lost everything. All you had fought for was gone. All that you had strived for had gone un-fulfilled.
Well, it's happened to Jake. He has awoken to find, to his surprise, that he's 25 years of age in a world where the Yeerks have won. Now he doesn't know who he can turn to. He may not even be able to trust his fellow Animorphs....