Who is Owl Eyes? What surprises him about Gatsby's library?

Owl Eyes is the name that Nick gives to a "stout middle-aged man" with "enormous owl-eyed spectacles." Nick meets this man at Gatsby's house in Chapter Three when he wanders into the library with Jordan while attending a party.

Owl Eyes is surprised by Gatsby's library because the books are real, a fact which he clearly did not anticipate, as we see from his verbal reaction:

“Absolutely real — have pages and everything. I thought they’d be a nice durable cardboard."

Owl Eyes notices, however, that the books have not been read, since the pages are "uncut." Nevertheless, Owl Eyes is seriously impressed by Gatsby's "thoroughness" and "realism" in creating an image of being educated and refined when, evidently, Jay Gatsby does not read books. Owl Eyes is so impressed that he likens Gatsby to David Belasco, a prominent theatre director of the 1920s. This suggests that Owl Eyes believes Gatsby to be a fraud, though the level of his deceptive skill comes as a pleasant surprise.