When you read a newspaper, you're going to understand 100% pretty easily, but of that roughly 95% will be fluff or filler. It is a rare exception when a newspaper article has more than one or two nuggets of actual "value", and even that value will likely expire easily within a weeks time. Contrast that with a book like The Road to Reality. There are very few people I think who could understand this book in its entirety, and to a reader on my level 50% may even be generous. But of those pieces which do make it through the haze, the density of value (such a subjective term) is on a scale so far removed from that of a newspaper that even one of Penrose's chapters could outweigh a years worth of daily study of the Times. Not only is the information content extraordinarily high, but what subject matter could possibly be more timeless and universal than the mathematics behind and the laws of the universe itself?