 But she noted that as she gets older, she's realizing that there are more and more and more books out there and that she's never going to get to them all. So she added a little corollary to her rule of 50. And it goes, when you're 51 years of age or older, subtract your age from 100. And the resulting number, which, of course, gets smaller every year, is the number of pages you should read before you can guiltlessly give up on a book.