I didn't do it. I asked a few cow orkers and they plead innocence ... I believe them; it's far too strange of an action to think it's a practical joke. The custodians might have, but I'm sure that they know the correct orientation for a book on a shelf: spine out. Weird.
The books are visible from the hallway outside my office, because that wall is a giant window. So considering one of the books is titled "Patents for Beginners," I guess my boss might have done it. :) But why all of them? That's a bizarre sense of consistency.
I feel like a page out of a Pottery Barn catalogue or that one bookstore scene in Eternal Sunshine. Weird!