His early novels were in the tradition of boys' detective stories with more than a dash of gothic mystery. Soapy and the Pharaoh's Curse was the first (1957) and this, along with two further Soapy adventures and a novel set in Ancient Greece, enjoyed moderate success. through the sixties and seventies he turned to writing one-act plays for schools and fringe theatre which are still performed today. They combine an acute ear for dialogue with a delight in the burlesque and could be described as pre-Python Pythonesque.
The plays prepared the ground for his foray into teenage fiction in the eighties. Young Man of Morning was accepted by Phyllis Hunt at Faber and Faber and published in 1979. Her editorial sympathy encouraged Lillington to develop his writing for older readers, and he started writing "ghost stories" - psychological novels in which the resolution usually lay in some healing, existential epiphany in the life of the chief protagonist. The best of these was Isabel's Double (1984), featuring a heroine struggling with an unwanted doppelganger.
Then he invented a genre entirely his own with An Ash Blonde Witch (1987), combining the English surrealism of the plays with the mystery and sophisticated plotting of the previous novels. The result was light but fantastic, crammed with literary allusions but retaining a genuine feel for character. A series of novels in similar vein followed - Jonah's Mirror (1988) and Josephine (1989) were dazzling in their accomplishment - and they represent some of the wittiest, most intelligent writing for young adults in the past decade. His last published novel, A Trick of the Dark (1994) was a gothic examination of myth and creation.
Twice short-listed for the Guardian Young Fiction Prize, Kenneth Lillington also enjoyed international success. His novels have been translated and published in Denmark, Germany, Spain, Italy and Japan.
Working with him as his editor at Faber from 1987 was a delight and a challenge. His contribution to children's literature was immense. He will be remembered as an author whose disciplined but fluid style combined seamlessly with unusual, even eccentric, plots and an intelligence that arose from a profound knowledge of, and love for, English literature.