THE STORY OF THE 9/11 COMMISSION (FROM THEIR PERSPECTIVE)
The "National Commission on Terrorist Attacks Upon the United States" consisted of five Democrats and five Republicans, and lasted from November 2002 until its final report was issued in August 2004 (shortly before the 2004 election). Arguably having been "set up to fail," the Republicans had wanted it to last for only one year (Pg. 20), and initially allocated only a paltry $3 million for it. The Bush administration strongly resisted having National Security Adviser Condoleezza Rice testify under oath in public, although she ultimately did (Pg. 110).
Among other things, the Report revealed how the inability of the FBI and CIA to share information hampered intelligence-gathering; how two of the hijackers known to the CIA had lived openly under their own names for several months; how an FBI memo warned that the matter of Arab men receiving flight school training needed to be looked into; and how Zacarias Moussaoui had been arrested in Minnesota just weeks before 9/11, and "described as a terrorist suspect with an interest in flight training." (Pg. 16)
It also pointed out the "massive intelligence failure" in assessing Iraq's prewar weapons of mass destruction, as "American forces occupying Iraq found none of the predicted stockpiles of chemical or biological weapons." (Pg. 129) It strongly criticizes the FAA passenger screening, as not only "permeable," but "aimed at keeping bombs out of baggage, not at keeping planes from being turned into guided missiles." (Pg. 138) National terrorism coordinator Richard Clarke (whose book Against All Enemies: Inside America's War on Terror came out during the hearings) argued in his testimony that "President Bush and his top advisers had not taken terrorism seriously before 9/11." (Pg. 154)
The Commission was dismissive of "conspiracy theories" (Pg. 252-255), concluding that after their actions (such as clearing up "inconsistencies in the FAA and NORAD accounts of 9/11"), "Those who chose to continue believing conspiracy theories now had to rely solely on imagination, their theories having been disproved by facts." (Pg. 268) [Which 9/11 "Truthers" dispute; see David Ray Griffin's The 9/11 Commission Report: Omissions And Distortions, for example.]
The report itself is available ('The 9/11 Commission Report: Final Report of the National Commission on Terrorist Attacks Upon the United States'). Another useful book is 'The Commission: The Uncensored History of the 9/11 Investigation.'