It's a hoot. The author does an excellent pastiche of Rowling's writing, but approaches a Muggle's induction into the wizarding world from a place of far greater surprise than the original Harry Potter's. He's so bowled over that his entire universe is turned upside down when he sees Professor MacGonagall turn into a cat. This makes no sense, it breaks ALL the rules, it is flatly impossible. But rather than deny it, this Harry Potter immediately starts testing everything he learns about magic using rigorous rational methods. He ruthlessly examines himself (and his peers) for biases, he endlessly pushes the limits of even the simplest of assumptions and magic spells. And he starts planning big - right away. As a result he gets sorted into Ravenclaw, brings Hermione along with him (where, let's face it, she belonged) and sees the Gryffindor "wanna-be heroes" as silly, as well as their favorite game, Quidditch, which he immediately dismisses as a distraction. Oh, and he thinks Ron Weasley is a dolt, but Draco Malfoy - well, there's a lad with some promise, if he can just be brought around a little.
Harry's biggest challenges are his own tendency towards Dark Lord-ism, after all in his first day at school he figures out how to dominate the economies of both the real world and the wizarding world, how to revolutionize Quidditch, and several other earth-shaking ideas. All with an eye towards, well, not so much ruling the universe, but at least optimizing it. With science!
I've never really read or enjoyed fan-fic before, for a variety of reasons. In fact I don't like most "borrowed universe" writing at all, as your average Star Wars novel is really just fan-fic with an editor and a license. But this is different. I'm immediately reminded of my own failure in recent years to question, test and analyze the world around me. I've become intellectually complacent, or at least mostly so, and this simple yarn has reminded me of how much more interesting the world is when you're looking for answers instead of short-cuts.
If you have any interest in Harry Potter, and particularly if some part of you was always disappointed that Harry didn't get his Hermione... check this out.