What is the theme in Misery by Stephen King?

Fanaticism is a theme in the book. Annie Wilkes is a mentally unstable woman who lives for a fictional character named Misery Chastain. Annie's life is one of hard work on a farm and basically a fugitive from her own past. Misery offers Annie an escape into the 19th century which was a softer gentler time when people did not behave like they do now.