Williams wrote several non-fiction books on intellectual and developmental conditions, especially on the autism spectrum "Autism – an Inside-out Approach: An Innovative Look at the Mechanics of Autism and Its Developmental Cousins" (1996), "Autism and Sensing: The Unlost Instinct" (1998), "Exposure Anxiety - The Invisible Cage: An Exploration of Self-Protection Responses in the Autism Spectrum" (15 September 2002), and "The Jumbled Jigsaw: An Insider's Approach to the Treatment of Autistic Spectrum "Fruit Salads"" (2006).