When I started writing Post, I didn't know of anyone else even attempting a book on post-hardcore/emo's history. Nothing Feels Good was on store shelves, but that only presented a superficial glance filled with typos. I always hoped more people would come out of the woodwork and write portrayals of how things were back in the proverbial day. As the years went on, I heard about Norm's book, Brian's book, Trevor and Leslie's book, and Ronen's book, and was relieved to find out we were all coming from different angles, writing distinctly different books. Still, there's been a fear of somebody putting out a book almost exactly like your book, at the almost exact same time. It takes thunder away and it can scare off readers. I know about this topic all too well as a reader myself.
For me, I usually read only one definitive book on a band, mainly to know their basic story. In the case of Nirvana, I haven't read Heavier Than Heaven, Journals or Nirvana: The Biography because Come As You Are was the only one written and completed before Kurt's death. Plus, I haven't heard the kindest things about Heavier Than Heaven and I really have no interest in Journals or Nirvana: The Biography. On top of that, I liked Azerrad's approach with Come As You Are and have had no interest in reading a book written after Kurt's death. I figured reading the other books would be redundant and less satisfying.
The same could be said for Chris Salewicz's biography of Joe Strummer, Redemption Song. Even though a friend of mine gave it an enthusiastic recommendation, I've had some hesitation since I read a very detailed biography of Strummer's life before the Clash and during the Clash called Passion is a Fashion: The Real Story of the Clash. Of course, Salewicz's book covers Strummer's post-Clash life more extensively and that's always intrigued me. But still, do I really want to read another take on John Mellor's transformation from a busker named Woody to Joe Strummer? Not really. (Then again, maybe I should just quit nitpicking, find a super-cheap used copy and skip to the post-Clash part . . .)
The point remains: as a reader, do you really want to read essentially the same band story over and over again? I guess that's what can scare off a lot of potential biographers and readers. I mean, I'm essentially up a creek if I ever wanted to read a definitive biography of John Lennon, Bob Dylan, Elvis or Brian Wilson given the plethora of books written on them. I doubt the post-hardcore/emo scene will get to that point, but you never know.