Of course, what's most interesting is the content. What it represents is the number of copies each of the top ten titles has sold in the past fifty years. That is sold, mind you, not read. There's a big difference. Of these top 10 titles, six are works of fiction (seven if you're an atheist), with the top and bottom two falling into the non-fiction category. The top and bottom are works of an historical nature, while the second to the top and bottom fall into the "inspirational" category, at least in intent (and only if you find these subjects inspiring, of course). Six of these works were originally written in English, and all but The Holy Bible within the last century. Nearly all of the popular fiction works fall within the past fifty years, within the time frame that the statistics take into account (or very shortly before that) - only The Lord of the Rings and Gone With The Wind are older than that - while the three most well recognized by modern readers fall into the "pop culture" bin of the most recent two to three decades (these being Harry Potter, The DaVinci Code, and The Twilight Saga, the most poorly written of the bunch, and of modern literature in general).
Conversely, all of the non-fiction works are more than fifty years old, save for Mao's Little Red Book (otherwise known as Quotations from...), which was first published in 1964. Think and Grow Rich was issued in 1937 and continues to be the best-selling "get rich quick" treatise on the market, and will likely remain so for as long as there are people who want to get rich just by thinking about it (the book, of course, is not about getting rich quick at all, but that seems to be what everybody thinks it's about). After all, it costs nothing to read (if you're a patron of the local library, that is), and even less to sit around thinking about getting rich all day.
My bet is that the three "pop culture" titles will fall off the list within the next ten years, while the more well-crafted works will remain, at least until equally well-crafted and deserving works appear. The influence of The Lord of the Rings has only grown with time as readers discover its astonishing depth and complexity, while Harry Potter's influence will likely wane as the legions of fans outgrow their childhood (if not their fifth grade reading level) and The Twilight Saga becomes gradually indistinguishable from the hundred other vampire-werewolf romance novels out there. Of the "pop culture" trio only The DaVinci Code will have any lasting impact, due not only to its controversial subject matter, but also its pseudo-historical context, which proves ever relevant and fascinating for conspiracy theorists of a literary bent (and there will always be boat-loads of those). The Alchemist is a bit of a dark horse here, being a truly unique entry among these titles, as both a work of fiction and an inspirational self-help allegory. It's hard telling what a book like this will say to people from one generation to the next. It's difficult to say what it means to people today.
As for the other non-fiction works, Mao's book will disappear as soon as he does (i.e. not soon enough), and Gone With the Wind will be just that, as younger generations fail to find an interest in outdated fictional history (read: stuffy and irrelevant). Anne Frank, of course, will have a lasting impact on the history of civilization, of the type that only grows with time and perspective - up to a point, at which it becomes ancient history, and no longer poignant (after all, who reads Caesar these days?). But that won't happen in our lifetime, because for at least the next century WWII will remain recent history, all too close for comfort. What will become of The Holy Bible is anyone's guess. Religion is a fickle mistress.
What would be more interesting here, to my mind, would be a comparative statistic of how many of these purchased books were actually read. The graphic's caption makes the distinction between number of books printed and number actually sold, but more important is the number actually read, a figure unfortunately impossible to determine. My guess is that more than half the Bibles lying around have barely had their covers cracked, while nearly every copy of Harry Potter has long since become tattered and dog-eared. The vast majority of purchased Bibles are bought in bulk by churches and related ministries to give away to third world nations and stock the drawers of cheap hotels. Additionally, there are hundreds, if not thousands, of variations of the Holy Bible, from tiny pocket editions in condensed form to fully annotated comparative editions in multi-column translations. All those count as a Bible sold. Still, 3.9 billion is a lot of books in any form. Too bad the author's not around to get those royalties.