He didn't specify the order (or/and script, if you prefer) in which the books were placed, so it's ambiguous.

Tomes of Pushkin have a natural order ascending from left to right. It may be a cultural thing, but it would be obvious for any Russian child 5 years old or older. No tricks here.

But, yeah, even knowing about the natural order of Pushkin on the shelf, I also gave it a thought. I was wrong and just wasted my time. It is an easy problem, without any tricks.

The same order a multi-volume set would be displayed in any bookstore or library in a left-to-right ordering country.