My first readthrough of DAYD, it struck me as very well written and thought-provoking.
But really, the story is EXTREMELY dark in both tone and events. Snape is a Complete Monster
(going against everything we know from canon), even in the dark.
He makes Voldemort look merciful, just to give you an idea.
The whole "detention with Hagrid" in the book becomes "sent in the Forbidden Forest wandless, WITHOUT Hagrid (???), and straight into a pack of very hungry werewolves...on the full moon. Keep in mind, that punishment was invented entirely by Snape. Powers As The Plot Demands
is the only reason they survive, and when they do, Snape is furious.
But Snape is just one aspect of the glaring differences between canon and this story. As soon as canon and this story intersect, things are normal. But the moment they don't, things are back to Beyond The Impossible
levels of darkness.
Other things are very glaring. Like why families even consider sending their kids back to Hogwarts the second term after hearing about their kids being horrifically tortured routinely (seriously, none of this even makes any sense), or why the DA decides that martyring themselves at the end of the school year is the best idea ever heard, and agree to it within seconds.
In short, a nice read, but so against canon in so many ways that you should NOT consider this in your "head canon" for outside of Harry's POV.