It's an amazingly written, exciting story, but if you don't want to permanently damage your soul, I recommend to read it only until the part when Harry arrives, and there switch to his point of view from Deathly Hallows. The majority of he story is perfectly fitting with canon, but unfortunately, at the end the writer really stretches this with assuming that (minor spoiler:) the canonical 50 casualties included almost ALL named characters who are not protected by explicitly mentioned survival in the canon, except for a few main characters of the story. Even some of those die who you would expect to stay alive, like: (massive spoiler:) Cho, or Dean, surely they are important enough that you would expect Harry to notice if they would be dead in DH, or Lavender Brown, who was explicitly mentioned as only injured, so Thanfiction just assumed that she bled to death a few seconds later, etc.
In short, it turned the original Bittersweet Ending into an outright Downer Ending. That would be fine, if you can treat it as an original work, but since it is so well fitting with canon, it plants a whole Inferred Holocaust into Deathly Hallows where there was none, and so it can be Ruined Forever if you preferred the happier ending.