Reread Books? Rewatch Movies? Why?

This week's Long & Short Reviews prompt asks whether reviewers actually re-view material we've already read (or watched or listened to), and why. 

I'll re-watch any movie because, while watching movies all by itself puts me to sleep, watching other people watch movies engages my brain. I know the plot of The Sound of Music pretty well, but if you want to watch it I'll enjoy seeing whether you, too, can sing along with the songs, or have somehow managed not to see this popular movie before. 

I'll reread a book if I want to spend more time with the author and characters. Joan Aiken, Dave Barry, Lewis Carroll, Pamela Dean, Suzette Haden Elgin, Richard J. Foster, C. Gockel, Nat Hentoff, Washington Irving, Ken Jennings, Carol Kendall, C.S. Lewis, Margaret Mahy, E. Nesbit, Ruth Ozeki, C. Northcote Parkinson, Anna Quindlen, Conrad Richter, Dorothy Sayers, Henry David Thoreau, John Updike, Cynthia Voigt, Alice Walker, Malcolm X, Charlotte M. Yonge, and Elizabeth Zimmermann are a short list of writers whose books have seemed worth rereading. Some books have seemed to need to be in my home for a year or two; some are dear friends I really want to keep around and revisit every few years for as long as I'm able to read. 

(Are some of those writers on the list only because their names start with underused letters? No such. Anna Quindlen and Malcolm X don't have as much competition as writers whose names start with more popular letters to be on an alphabet list of writers whose books I've reread, but they have earned places on the list.)

I'm likely to buy books only if I think they're worth rereading. When one reading is enough, that's what public libraries are for.