A Secret History of the 9/11 Investigation
propublica.org
propublica.org
If you just read the report, you can immediately see that it is written as a novel, not a scientific report. And the commission itself complained about a set conclusion and not being able to do a proper research.
Also many witnesses complained about their story being left out of the report. Also: omission and even destruction of important evidence.
Whatever happened, the investigation was a white-wash and has been misused to setup a political system for needless endless wars. Like the Reichstag fire.