Animorphs #17: The Underground

In this story, Rachel and the other Animorphs now know a secret to stopping the Yeerks.  The bad news is that the Yeerks get addicted to it.  And the thing is: oatmeal.  Now the only thing they have to is find a way to feed it to the Yeerks.  My favorite part of the story was when the Rachel  pretended to be a 25-year-old.  I liked this story because it was entertaining.