Yes, "The Witches" was written by British author Roald Dahl (illustrated by Quentin Blake) and first published by Jonathan Cape Ltd in 1983.

Roald Dahl is known for his writing of other famous children's books (many of which have been made into movies) including: James and the Giant Peach (1961; adapted as an animated film in 1996), Charlie and the Chocolate Factory (1964; adapted as a film twice, in 1971 and in 2005), The Magic Finger (1966; never adapted), Fantastic Mr. Fox (1970; adapted as an animated film in 2009), Charlie and the Great Glass Elevator (1972; never adapted), The Enormous Crocodile (1978; never adapted), The Twits (1980; never adapted), George's Marvellous Medicine (1981; never adapted), The BFG (1982; adapted as an animated film in 1989), The Witches (1983; adapted as a film in 1990), The Giraffe, the Pelly and Me (1985; never adapted), Matilda (1988; adapted as a film in 1996). Dahl also wrote a number of books of children's poetry, including: Revolting Rhymes (1982) and Dirty Beasts (1984), and several collections of short stories, such as The Wonderful Story of Henry Sugar and Six More (1977). He also wrote a two part autobiography, Boy: Tales of Childhood (1984) and Going Solo (1986).

They have a purple tinge to their eyes; no toes which they hide under plain sensible shoes; they're bald and due to irritation from wigs, will have an itchy scalp rash; they have claw-like finger nails and many have what looks like inflamed, blistery skin on their hands; and they also have a very good sense of smell that helps them locate children that they prey upon (which to them smell strongly of fresh dog's droppings). They also never get caught committing their crimes as they dont use knives or guns like ordinary people, but instead use spells and/or special powers. Examples include the children imprisoned in the two paintings; the snake charmed by the witch below Luke's tree house, and its subsequent disappearing and reappearing into her purse; the Grand High Witch's killing of the other witch at their annual meeting; the Grand High Witch's assistant transforming Luke from a mouse back into a boy again, and her the ability to make William and Mary the mice float up and pop into their cage again, as well as Luke's glasses pop back onto his head out of thin air. We also know that every country has their own head witch, all ruled over by one Grand High Witch.

Formula 86 is a potion created by the Grand High Witch, that when ingested, causes one to transform into a mouse. It was designed to be used only against children, but anyone, including adults and witches, who consume it will transform as well. Each bottle contains 500 doses and one dose will take exactly two hours to begin the transformation process. Once the transformation process begins, it will take precisely 25 seconds to complete. The afflicted individual will first loudly burp, then begin to expel green smoke out of their mouth, shake, grow fur, a tail, shrink, and ultimately change into a mouse of varying colors/patterns. If one were to consume more than five doses at once, the transformation process begins instantly.

This movie was slightly cut in the UK to get the PG-rating. It's at least questionable whether these 2.5 seconds actually would have been the reason for not getting the PG-rating.