Time for some more advice on writing a book. These two ideas come from talking with a couple of people who have just begun writing their own books, and I hope you can find inspiration as well.
Imagine your ideal reader
This is crucial because it affects the overall tone of your book. Are you writing a book for people who know everything about the topic or know nothing at all about the topic? Know your limits, and don't be afraid to explain yourself. You have plenty of space to explain.
For Post, I wrote it in a way that people my age would understand, but not strictly for people my age. Whether you put on a show for Hot Water Music at a rehearsal space, bought Braid's first few 7"s by mailorder, saw At the Drive-In in a small VFW hall, or saw the Promise Ring's "Why Did We Ever Meet?" video once on 120 Minutes, this book was written with those kinds of people in mind.
I did not want to come across as one of those elitist, "since you weren't there you'll never understand" types. Rather, this was my attempt to explain how and why people like me still think highly of bands like Fugazi, the Promise Ring, and the Get Up Kids and are probably disgusted by mall emo bands. So, taking some inspiration from a couple of documentaries that save bitter ranting and raving until the last few minutes (Hype! and American Hardcore), I tried to make Post a positive retrospective.
Write your book, then think about how you're going to put it out
If you feel strongly compelled to write a book, don't let the worry of who will release it stop you. Even though my original hope of putting out my book on a friend's label fell through, I still wanted to put out Post in some form or fashion. When a few interested editors wanted me to completely jettison the heart and soul of the book just so I could have a book out with a name publishing house, I decided to self-publish.
My point is, expressing yourself and marketing yourself are two different things. In the planning stage they seem like they're one in the same. I disagree. Say what you want to say, then look into release options. And just because you get turned down by agents or editors doesn't mean your book is crap. That's your call.