Dahl’s beloved children’s tale, The BFG, was illustrated by his favourite artist, Quentin Blake, whose work is the subject of the new show.
It contains 40 original artworks, including rarely seen, unpublished illustrations of the giant, which provide an unusual insight into its creation.
A series of activities for children is running alongside the exhibition, at York Art Gallery.
Blake, who produced the drawings for most of Dahl’s children’s stories, as well as those of many other authors, said he had been made to create the pictures for The BFG twice.
“I was originally commissioned to produce a dozen illustrations,” he said.
“After the book had arrived at the printers, Dahl complained that there were not enough illustrations, and within a few days I produced more than 20 drawings.
“However, Roald was still not happy, and so that the pictures could run through the text in quantity, I went back to the beginning and started again.”
Those that did not make the final edition are among those now on display.
Kirstie Blything, at York Museums Trust, said: “This is a fantastic opportunity to see illustrations that were never originally published in the book, discover how The BFG developed and learn of how Quentin Blake and Roald Dahl worked together to bring us this larger than life character.”
Dahl wrote the story in 1982 and dedicated it his daughter, Olivia, who died, aged seven, of measles, 20 years earlier. The book has sold 37m copies and spawned a film version, directed by Steven Spielberg.
The exhibition, The BFG in Pictures, opens today and runs until late February.