French poet and mathematician Jacques Roubaud once proposed the following formula for maintaining an ideal book collection; by his working, 1 of 361 works: K + X > 361 > K – Z, where K = 361, X = a newly acquired book, and Z = a previously owned and since-relinquished book. While this formula amounts to a collection of books currently owned, rather than exhaustive cumulative tally of books read, it does at least set in our sights a number more manageable.