As a dark deconstruction of the wish fulfillment involved in Peggy Sue
and Fix Fic
plots, it's very good.
It is chilling and gut-twisting, and if you let yourself get too into it -which is disturbingly easy to do- you might end up questioning life itself and if it's futile -a primal fear.
Once the emotions pass, however, and Fridge Logic
kicks in, you start asking questions that were previously instilling fear and desperation through the story: Why is it all happening? For what purpose? Who is orchestrating this? Who or what decided that Harry couldn't leave England before school started or change the "plot" too much? Why was he unable to seek the help of others?
The question of "why Harry didn't try less extreme ideas and instead tried to break down the loop by doing small variations to test it and try to get around it" is solved by the fact that it's Harry, who doesn't take a very logical approach to problems, but the question of why it never occurred to him after earning the wisdom of several centuries of the same life over and over still remains. (Or maybe he went too crazy to try that.)
It's visceral and dark, and it follows the spirit of the story of Sisyphus very well, but the nagging questions it raises after reading it can help defuse the horror that they ignited at first.