This is a thoughtful and world-building departure from canon, building Harry's support system with Sirius and the Black family. Starting after the end of third-year, there's a twist which becomes apparent (through author's notes, which are augmentative and sometimes very useful, and other times not) and diverges pretty exceptionally from the same old terrible summer at the Dursley's-finish up at the Weasley's motif that we've come to expect.
Harry starts adjusting to having a godfather, Hermione's family is introduced more, Ron tries an independent study, and the Goblet of Fire has a very different impact on the Trio's 4th year. Dumbledore is just as manipulative as canon, but he's not the tropish "manuipulative old coot/goat", and there's no all-out war. Harry isn't super-powered, Ron's only as idiotic as normal 14 year old boys, and Hermione is still a know-it-all, but now she's a bit more than just that.
Highly enjoyable, I'm already reading the next in the series the glass fortress (Brilliant Difficulty #2). (Honestly, I'd read this before, and started glass fortress before, but it got buried in my bookmarks on AO3 and I forgot about it until I saw it come up again on reddit. I was glad to be reminded.)
It's a hard story to judge! It is pretty heavy story with all issues addressed. Almost every character has a lot of baggage and questionable decisions!
I enjoyed reading it. But I wouldn't recommend it to people who like soft 'everything-is-going-well' fix-it fics!
The brilliantly difficult series is a top contender for my favourite fanfic series. It's ambitious, and it sometimes fails, but especially if you read the one-shots, the author ties it together so well. Possibly the only AO3 author I will read no matter what.