Conceptually an easy five stars, but I must round down to, at most, four:
The author’s grasp on language is sometimes not good enough to bring their point across. Sometimes it’s just a weird sentence structure or a wrong or misspelt word, but sometimes it’s harder to read.
Even worse, they regularily lose themselves in in-depth descriptions, yet fail to bring out what actually happened. I was confused at multiple points in the story, for example (several chapters later, but it was extremely unclear at first). Adding to that, the author’s massive reluctance to “write out parts that [they] find boring” makes for a regularily unpleasing, tedious, read.
Surprisingly, the crossover part of the story gave me no trouble. It was only a slight one, and explained good enough (given the above). If anything, it’s given me incentive to read the actual Myst books.
The end was abrupt enough to almost drop it down even further, but it was overall good enough, and funny enough (bordering on crack though… but it does contain the best death of ever (even if a bit nauseating), and Dark Lord in the original universe being mentioned as a later aside Harry (in the new universe) gets informed of tops up the fun.