I just finished this book, and found it to be readable and engaging, although certainly not prefect.
One thing to realize going in: this book is just as much about SST as it is about Black Flag. If you cut out all of the not-Flag-specific text, the book would be probably half as long as it is. The two were pretty intertwined, so I have no problem with the inclusion of that material.
"Spray Paint…" makes heavy use of the books that came before, but Chick also conducted numerous interviews himself with many of the principal players in the Black Flag/SST scene. Keith Morris, Mike Watt, Joe Carducci, Tom Troccoli, Mugger and especially Chuck Dukowski really help to round the book out with interviews conducted in 2009. Brendan Mullen, Kira Roessler, Ron Reyes, Dez Cadena, and Mark Arm (among others) were also interviewed and have generally interesting and relevant things to say.
Main Flag man Greg Ginn was not interviewed, although I'm sure Chick tried. Instead, he pulls quotes and information from probably every interview Greg ever gave to a fanzine or newspaper to shed some light on his interpretation of events. As someone who has not read any of the previous Flag books besides "Get In The Van", I found these snippets to be very useful.
Henry Rollins was also not interviewed for this book, but fortunately his take on things is well documented, and Chick draws from a number of Rollins books and spoken word performances for background and details. And Chick dutifully cites almost every direct quote in the book - many come from the interviews he conducted, but when he does take something from another source, he gives the title or in many cases a full URL. This is much appreciated.
I do have some quibbles with the book, though. Besides referring to Misfits as a California band, Chick credits Henry Rollins' first post-Flag project to "Henrietta Collins and the Wifebeaters" when it is, of course, "Henrietta Collins and the Wifebeating Childhaters". And he repeatedly refers to Huntingdon Beach instead of Huntington Beach. These may seem like minor annoyances, but getting such basic and easily-verifiable information wrong casts some doubt over the information presented in the book as a whole. There are also a few typos (where is Irag?) and what appears to be at least one errant paragraph inserted in the wrong place.
Then we have the age-old problem of "writing about music is like dancing about architecture." Chick spends a lot of space describing Black Flag's music track by track, especially Ginn's guitar playing, and the descriptions get repetitive after a while. And no words can convey the emotional impact a particular song might have on you… You can hear previews of almost everything Black Flag ever released at the iTunes Store or Amazon's MP3 section, among other places.
One last piece of criticism. The front cover features a giant photo of Henry singing, but his name isn't even mentioned for the first 200 pages. Greg Ginn, the only constant member and focus of much of the book, is shown in a much smaller photo on the back cover. This was obviously done for marketing purposes, but could be a little misleading for folks who don't already know something about Black Flag.
Having said all of that, I did like the book. The most interesting part, for me, is the early biographical details of these folks, where they came from and how their lives intersected. Again, Rollins' story is fairly well known by this point, but I enjoyed reading about the others.
An index would have been great, but Chick does include a full bibliography. I would recommend "Spray Paint The Walls" to someone interested in Black Flag and/or SST; even if you have read the other Flag books, the new interviews alone may be worth the trudge.
BONUS: Check out this infographic, Black Flag Hair: A Timeline. Ha!