Just after Christmas I was contacted by John Granger, who has written a number of books on the Harry Potter series – FWIW, I've not read any of the books but I've seen two of the movies, the first one and some other one. He'd learned about Mary Douglas's work on ring composition and had determined that all of the Harry Potter books are rings and that the series as a whole is a ring. As I've not read the books I have no opinion about whether or not he's right, but it's certainly possible. Here's an interview where he talks about ring composition in the Potter books. Here's his book on the subject: Harry Potter as Ring Composition and Ring Cycle.
And here's a post where he argues that Mary Shelley's Frankenstein is ring composed and here's one about ring composition in Around the World in Eighty Days. He's sent me a document in which he describes ring composition in Robert Louis Steven's Kidnapped. I may have read Kidnapped years ago, but I've not read either Frankenstein or Around the World in Eighty Days.
This work, of course, raises the question that's been on my mind for some time: Just how wide-spread is ring composition? I have no idea.