To be honest, this is more of an essay than a book; you can finish it in a couple of hours or less.
However, I'm addicted to these survivor accounts, so for me, they're worth reading, and they're all certainly worth being documented in some form.
This is an account from Bruce K. Walch, a civil engineer who worked for the Port Authority at the North Tower. He came pretty close to losing his life: at 1015 he was trapped on the 10th floor and only just made it out before the collapse at 1028.
I'm giving this 3 stars rather than, say, 4, because it seemed like the author was holding back on details he may have thought a bit too gruesome to include. I say the realities should be documented.