I'm reading it right now. If you read it you would know what Bush is talking about.
The statement instantly comes to mean "Bush admitted he was mystified by the 911 report, and wondered out loud if it was a novel."
I finished reading the report day before yesterday. I was struck by the style of writing when it was describing the events surrounding and on 9/11. Someone put some effort into making it seem like a novel. It is actually well-written, easy to understand, until the Commission delves into their recommendations on the intel overhaul. That section seems almost to be an afterthought compared to the rest of the report. I am going to assume that section was subject to many rewrites in an attempt to get their precious unanimity.
But Bush is actually spot on when describing its style.