A Tale of a Tub
Robert Hendrickson notes in his book "British Literary Anecdotes" that "Swift was always partial to his strikingly original "The Tale of a Tub" (1704). On reading the work again in later years, he exclaimed 'Good God! What a genius I had when I wrote that book!'"
A Swiftly Tilting Planet
Matthew Maddox's second novel, "The Horn of Joy" (1868), serves as a MacGuffin in "A Swiftly Tilting Planet". Charles Wallace spends a significant portion of the book trying to remember or discover what Maddox wrote in it, or to reach Maddox himself. Readers sometimes wonder whether "The Horn of Joy" ever existed; but it is a fictional book, created by L'Engle. Polly O'Keefe finds a copy of "The Horn of Joy" in her room (formerly Charles Wallace's room) when she visits her grandparents in "An Acceptable Time". Maddox's equally fictional first novel, "Once More United", is said to have been published in 1865.