First, let's be clear: we're talking about the translated version of this story. If you want to read it in the original Spanish, you might want to bump this up a few notches on the tough-o-meter (unless, of course, you read Spanish – in which case, you totally should read this in Spanish).
Our buddy Borges has a thing for long, super-packed sentences. Combine that with some random magical elements and a lot of esoteric references (Maimonides and Virgil's fourth eclogue, anyone?) and it makes for a pretty challenging read. But it's well worth it: the images that Borges creates are unforgettable. Plus, reading Borges just wins you automatic cool points.