In a 1941 letter to a student, the great novelist C.S. Lewis delivered some advice that should apply to all readers and writers: “Your book bill ought to be your biggest extravagance.”

How much do you spend on books? One Reddit user made an online poster to frame the quote (embedded above)–remember Lewis’ words the next time you are debating buying something at your local bookstore.

The CS Lewis Society of Frederick, Maryland has more about the quote: “From a letter dated April 8, 1941 to Derek Brewer from C.S. Lewis regarding the books he should read to prepare for his time at Oxford, where Lewis was to be his tutor. Found in the Collected Letters of C.S. Lewis, Volume 3, in the supplement, page 1540-1541 in my hardcover copy.  I first discovered the quote in Words to Live By: A Guide for the Merely Christian in the section on Books.”