However, there are some clues we can look at:
* He was known to love classics: Dahl was a big fan of authors like Charles Dickens, Rudyard Kipling, and Mark Twain. These authors influenced his own writing style and his love for storytelling.
* He admired books with strong characters: Dahl often spoke about his admiration for books with memorable characters, like "The Wind in the Willows" by Kenneth Grahame.
* He was fond of fantasy and adventure: Dahl was drawn to stories with a sense of wonder and imagination, like "The Lord of the Rings" by J.R.R. Tolkien.
Ultimately, while we can't know for sure what Roald Dahl's favorite book was, it's likely that it was a book with captivating characters, a compelling story, and a touch of magic and whimsy.