It makes me somewhat dissatisfied with my collection now especially the number of Jack Vance titles he has, although I can beat him on his A E Van Vogt’s.
By the look of it (like my own collection) many of those books are second hand, probably the only way to get a lot of those titles nowadays.
At least he has big holes in his collection. Of course that’s probably because he’s so busy moving on to the next book that he just doesn’t care…
I have to wonder how he buys new books. He’s got a couple of used book stores worth of stock there so he’s got to have something to avoid buying the same book over and over again.
Bigger and better organized. I am beshamed. 
I think my own style edges more towards the wizard/mad scientist’s study. More than a far share of books, offset by cobwebs, skulls, and scattered lights flickering in the dark between vines of cable.
Only one of the skulls is real, to boot. And it’s not even the one wearing a hat. Double .
Just barely glancing at the photos, a triplicate caught my eye (The Spirit, IIRC-- it was yesterday); it couldn’t have been unique.
I think you might have spotted different volumes of The Spirit Archives, but that’s just a guess. The only thing I spotted multiple copies of were his own books.
You’re right. On second look, there are 4 of them, labeled 1, 2, 3, 4. If he employs a librarian like someone upthread suggested, I’m sure he or she takes care of dupes.
He gets a number of books from publishers for various reasons. If you read his blog, he’ll sometimes show you a table stacked with the goodies he’s gotten.
Gaiman’s got nuthin on this guy: