It's to illustrate a Wikipedia article called List of fictional books. A fictional book is a book referred to inside a fictional work, a book that (usually) doesn't really exist. I say "usually" because sometimes an author creates the book after the fact - but the fact remains that it's a fictitious book by a fictional character.
In my graphic above, C.S. Lewis postulates a number of amusing titles for books owned by Mr. Tumnus the faun in The Lion, the Witch and the Wardrobe. That's one of the things I love about fictional books. Much of the time, they have great, funny, intriguing titles.
Heck, a lot of the humor in the books of Douglas Adams comes from fictional books, from the text of the fictional Hitchhiker's Guide to the Galaxy itself to the "philosophical blockbusters" of Oolon Colluphid:
- Where God Went Wrong
- Some More of God's Greatest Mistakes
- Who Is This God Person Anyway?
- Well That About Wraps It Up for God
And from time to time, people ask me about a book called The Horn of Joy by Matthew Maddox, a book mentioned in A Swiftly Tilting Planet by Madeleine L'Engle. The Horn of Joy is a crucial plot element in the novel, a book Charles Wallace needs to know more about in order to save the world. L'Engle gave it so much verisimilitude that readers sometimes wonder whether The Horn of Joy is a real book. It isn't.
I must go read five chapters of a real book now and go to bed. I've got a Confirmation class in the morning. I was already confirmed as a Roman Catholic 36 years ago, but I'm going to be "received" as an Episcopalian. But first I have to read John 13 through 17. Good night!