Stephen King
In this book, King offers advice to aspiring writers, drawing on his own experiences. As such, King himself can be seen as a character in this text, as he is inspired by his personal life. For example, in the section "C.V," King tells us about his early experiences that inspired his writing. At the end of the book, he tells us about a van accident he was involved in, which changed his perspective about life and writing.
The reader
King addresses his reader directly in the text, offering advice and support for writing. For example, he tells the reader the "adverbs are not your friends," and throughout the text engages with his reader as if they are someone he is speaking to.
King's Wife
In the section "C.V," King talks about his relationship with his wife, and how it has inspired his writing.
King's mother
When writing about his early experiences in the text, King tells us about his mother. He tells us that the death of his mother affected him considerably, and inspired his writing.