The Whalestoe Letters

This story is included in an appendix near the end of the book, as well as in its own, self-contained book (with additional content included in the self-contained version). 

It consists of Johnny's mother's letters to him from a psychiatric hospital. 

The letters start off fairly normal but Pelafina quickly descends into paranoia and the letters become more and more incoherent. 

There are also secret messages in the letters which can be decoded by combining the first letters of consecutive words.