Some time ago, I read Dumbledore's Army and the Year of Darkness. If you've been hanging around HP fan fiction communities at all (anywhere except MNFF, which by the way I think should stop trying to pretend they're the only site where HP fan fiction exists, since I really don't think your Mugglenet overlords are paying attention anymore anyway), you've probably heard of it. It's written by thanfiction, who has accomplished the fairly remarkable feat of becoming a BNF in HP fandom after the end of the series and the fandom has begun declining. thanfiction has written a bunch of prequels and sequels and vignettes now, and the "DAYDverse" apparently has spawned LJ communities and fan fiction of its own. Pretty impressive.
DAATYOD tells the tale of Neville and the D.A. during their seventh year. It's the story about what was going on back at Hogwarts under Snape and the Carrows, while the Trio was on their camping trip.
I found it to be pretty good. thanfiction is a good writer, and the story was riveting at times, though occasionally too self-indulgent with the blood and angst and horror. It was definitely not written in the same tone as Rowling -- Snape and the Carrows do truly horrific things to the students, which are gruesomely described -- which really shows when Harry finally comes back for the final battle.
But, there's a reason why whenever someone asks for fan fiction about Neville and the D.A., this is the one that almost always gets recommended.
I stopped reading the sequel, Sluagh, about halfway through, because I thought the story was beginning to bear no resemblance whatsoever to Rowling's world. Nothing wrong with that, per se, but while I think thanfiction is a good writer, he's not so good that I'm interested in his original fiction. Also, he seemed to be trying to escalate the level of blood and grit from DAATYOD, until Sluagh became almost carnographic at times.
I followed thanfiction's LJ for a while. He seemed like an interesting guy, but there was something... odd about some of his stories. I couldn't quite put my finger on it. He claimed to be a barista at Starbucks or something, and he was always a step away from living on the streets. I seem to recall he claimed that he'd spent weeks living in his car. He also mentioned at one point that he was always buying drinks for combat veterans back from Iraq, just so he could sit and listen to their tales, to add more verisimilitude to DAATYOD.
I got the feeling that he was, perhaps, embellishing his life story a bit, because things just didn't quite add up. Eh, whatever.
He also was a bit wanky. He posted a rant on fanficrants once about how PO'ed he was that someone was using "his" version of Terry Boot (from DAATYOD) in a way he didn't approve of.
Okay, I sympathize. I'd be annoyed to discover people writing bad fan fiction about Alexandra Quick, too. But I also recognize that legally, there's diddly squat I could do about it, and really the only reasonable action I could take is to ask the author to knock it off. If Rowling suffers the existence of Snarry fics, I think it's a bit pretentious for HP fan fiction authors to act as if they own "their" versions of her characters.
Then thanfiction announced that he had hardcopy versions of his fan fiction for sale on Lulu.
Fan fiction... for sale.
He claimed that he was charging only printing and shipping costs just to make the hardcopy versions available to those who wanted them. Now, when several people (including me) pointed out that you still can't charge money for fan fiction you effing idiot!!!, he took them down. Still... how do you become a BNF and not grasp this essential principle?
Well, whatever. He's a decent and very prolific author, he has a large fanbase, and he's kind of prone to doing stupid shit.
Boy, I didn't know the half of it.
I find this epic wank fascinating, and a bit tragic. From what I've seen, this person has legitimately earned BNF status in more than one fandom. And yet, a trainwreck.