The Visitor
Plot:
One of Rachel's best friends, Melissa, is acting very strange. And it looks like Melissa's dad, who is also the school's Assistant Principal, may be connected to the aliens. Rachel can't tell Melissa what the ANIMORPHS have learned, but Melissa doesn't seem interested in talking to Rachel these days anyway. Could Melissa be one of "them?" Rachel plans to enter her friend's house as a cat, intent on unlocking the secrets from within. If only Rachel could keep her mind off mice...
Comments:
This is often cited as the least of the Rachel books, containing practicaly no development of her conflicting, paradoxial, personality. But remember that this is only #2: first K.A. has to set the stage for that, and this book does a good job at subtly bringing up various points such as Rachel's identification with the shrew and the cat. It also points out various intimate family details that normally no one would think about in a kids-against-aliens scenario, and sheds more light on the workings of the Yeerks.