This is a risky and brilliant title. The Enchanted Hunters is the hotel where the predatory monster Humbert Humbert has his way with the nymphet Lolita. Maria Tatar is the author of the excellent Hard Facts of the Grimms' Fairy Tales as well as works on the Bluebeard story, Hans Andersen, and sexual murder in Weimar. Enchanted Hunters is not about classic fairytales but about authored children's writing, what children take and need from stories, and how this is not always what parents imagine.

Tatar begins with a wry analysis of how stories have the opposite effect from the desired one of making children drowsy and ready for sleep. She is splendidly contemptuous of books such as Disney's three-minute Bedtime Stories, Condensed Fairy Tales and even One-Minute Greek Myths. Good stories excite, delight and frighten. They are, as Tatar puts it, a solitary addiction, not necessarily teaching sociability or virtuous behaviour. Those of us who as children read late into the night under the bedclothes with torches know exactly what she means.

Children, she observes, do not "identify" with characters in stories. They inhabit the world of the tale, as lookers-on, learning brilliance and danger and horror in another world. There is a very good chapter on the imagined encounter with death and real danger. Tales such as Struwwelpeter (1845) "revel in images of bodily violence"; Andersen's Little Match Girl is frozen to death; the dancer in "The Red Shoes" dances on bloody stumps. Andersen is frightening as the Grimms are not. I have always thought we know where we are with the Grimms  in an unreal world with strict rules of reward and retribution  but Andersen is trying to distress his readers. (He didn't like children, as is often the case with children's writers.) One of Tatar's best and most subtle discussions is of EB White's Charlotte's Web, in which Charlotte the spider saves Wilbur the pig from slaughter by weaving words in her lovely web  and dies herself, after her success. Tatar shows how the tale is also about the power of words to weave a web of magic, to make both glamour and understanding.

She is very observant about the way in which the great storytellers construct what Tolkien and Auden called "secondary worlds"  worlds with their own inhabitants and landscapes, seas and shores, caverns and castles. She writes excellently about the inventors of Neverland and Wonderland  Barrie and Dodgson, those two childless men who constructed theatres of the imagination in order, as Barrie himself put it, to "hold on" to the attention of the boys he loved, or to entertain Alice Liddell on rowing picnics. Tatar quotes an amazing description by Barrie of the "more or less" island of Neverland with savage and lonely lairs, gnomes, princes  but also "first day at school, religion, fathers, the round pond, needlework, murders, hangings, verbs that take the dative, chocolate pudding day, getting into braces, say ninety-nine . . . and either these are part of the island or they are another map showing through, and it is all rather confusing, especially as nothing will stand still".

All children, except one, grow up, Barrie observed. Perhaps Tatar's most original contribution to thought about children's stories and what they do to their inhabitants is about how the addicted readers are also learning (most of them) to deal with growing up. The great powers of the mind in the world of children's books are a capacity for wonder, and an insatiable curiosity. The writers feed both with colours never seen on sea or land, with moons and stars and gold and silver and monsters and dangers. But they are also teaching mastery of language which is the stuff of thought and necessary to growing up when the time comes. A particularly telling chapter is called "The Great Humbug". It discusses The Wizard of Oz and what Dorothy learns from discovering that the great magician is in fact only a timid illusionist who makes an emerald city by handing out green spectacles. Dorothy ends the story by saying that she wants to go home to Kansas and Aunt Em  thus making herself alive in the real world. In the same way Maurice Sendak's child goes home, empowered in real life by his brush with the Wild Things.

Tatar has a particular fondness for Dr Seuss, the inventor of The Cat in the Hat, whose real name was Theodor Geisel. She addresses him in the context of a 1950s discussion of "Why Johnny Can't Read", which ascribed illiteracy and childhood boredom to anodyne reading primers. I didn't know before I read Enchanted Hunters that the publishers Houghton Mifflin had a list of 348 words that should be offered to beginning readers  and that Dr Seuss crafted The Cat in the Hat with the use of only 236 and a gripping, anarchic narrative.

The net is spread wide. There are shrewd observations on JK Rowling, CS Lewis and Philip Pullman and an excellent section on The Secret Garden. All these are praised for creating and satisfying curiosity with precisely imagined places and objects  Quidditch, the wardrobe, Mary's ferocious hunting through room after room in the huge house where she finds herself. There is a good description of Kipling's Rikki Tikki Tavi, but I should have liked much more about The Jungle Book and Puck of Pook's Hill, both of which I lived in as a child. If I feel a need to inhabit imagined worlds I prefer Tolkien and Terry Pratchett to Lewis  they do not, as Lewis does, "have designs on you".

This is a grown-up book for grown-up people who haven't forgotten being childhood readers. It satisfies imagination and curiosity, revisiting things you suddenly remember clearly, telling you new things you didn't know.

AS Byatt's The Children's Book is published by Chatto & Windus.