As is made very clear by the title, this is a sports-sim game set in the Harry Potter universe, many years before the events of the novels. Very short, it relies heavily on fairly obscure knowledge of its oeuvre, and makes little effort to supply it to outsiders. While the player has more influence on the match than in most recent sports-based IF works, the game-like elements are not deep, and non-enthusiasts are unlikely to find very much here. (As someone with only glancing knowledge or interest, I can't speak to how it treats its subject matter.)
The game shows pretty strong evidence of being written by someone without a strong familiarity with IF. Almost no descriptions are written, so EXAMINE is near-useless. The verb-set is limited to a small number of mostly specialist verbs during a short intro sequence, then even further limited during the game itself. The events in the game itself are heavily random. As the Gryffindor Seeker, you're responsible for catching the Snitch and ending the game; but victory in the tournament requires that you wait until your team is ahead by 30 points first. A few commands allow you to disrupt the opposing team, with random success, or avoid being disrupted. Otherwise, it's a matter of waiting until the right moment as the match plays out, then using the SEARCH FOR SNITCH command and hoping it works. With a little application of UNDO, victory is not difficult.
Much of the action takes place independent of what you're doing, and is not always very clearly explained. (Someone familiar with IF conventions would probably have included the game's score in the status bar, and made SCORE work as well as X BOARD.) Quidditch involves a lot of aerial acrobatics, so the interaction necessarily takes place at a fairly abstract level; thus also the description of events, and I never got a very strong sense of the physical state of the game; and character-wise, it relies upon the reader having a good established sense of who most of these people are, or who they will become. So I suspect that the game may be fairly unsatisfying even for Potter fen; as Emily Short has written of Ron Weasley and the Quest for Hermione, and as I've experienced with some of the movie-based Harry Potter videogames, a lot of the appeal of this kind of thing is about immersion in a familiar fictional environment. This is the sort of thing that IF is really well-suited for; instead, Quidditch Final brushes past environment exploration and character interaction, and aims straight for something that IF is traditionally very weak at: a complicated action sequence. So, while the author has definitely done their homework -- the thing bristles with throwaway references -- I'm not sure that it's employed to best effect.