Joint Inquiry"The Joint Inquiry into Intelligence Community Activities before and after the Terrorist Attacks of September 11, 2001" was released in December 2002. It comprised 832 pages according to Wikipedia.
9/11 commissionThe 9/11 Commission Report consists of 541 pages if you include the notes. Link to the official (but frozen) commission site can be found here.
NIST's investigationsNIST published reports on both the twin towers, WTC1 and WTC2, but also a report on WTC7. A list of all their final reports on these 3 buildings can be found here.
NIST's report on the twin towers was released in September 2005.
NIST NCSTAR 1-1 is 185 pages excl. appendices. NIST NCSTAR 1-1A is 130 pages long
N.N. 1-1B is 47 pages. N.N. 1-1C is 121 pages. N.N. 1-1D is 131 pages. N.N. 1-1E is 7 pages.
N.N. 1-1F is 5 pages. N.N. 1-1G is 33 pages. N.N. 1-1H is 59 pages. N.N. 1-1I is 17 pages.
N.N. 1-1J is 49 pages. N.N. in total thereby comprises 784 pages.
NIST NCSTAR 1-2 is 302 pages long (appendices is another 37 pages, but do not have to count them). N.N. 1-2A is 149 pages (with 42 pages for the appendices). N.N. 1-2B is 393 pages long. In total 844 pages.
NIST NCSTAR 1-3 is 134 pages. N.N. 1-3A is another 47 pages. N.N. 1-3B is 57 pages long. N.N. 1-3C: 287 pages (with 186 pages appendices!). N.N. 1-3D: 163 pages (110+ pages appendices). N.N. 1-3E: 125 pages. In total: 813 pages.
NIST NCSTAR 1-4: 99 pages. N.N. 1-4A: 15 pages (same amount for appendices). N.N. 1-4B: 173 pages. N.N. 1-4C: 109 pages. N.N. 1-4D: 113 pages. In total: 509 pages.
NIST NCSTAR 1-5: 184 pages. N.N. 1-5A: 417 pages (with 13 appendices comprising 544 pages!). N.N. 1-5B: 231 pages. N.N. 1-5C: 71 pages. N.N. 1-5D: 79 pages. N.N. 1-5E: 101 pages. N.N. 1-5F: 117 pages. N.N. 1-5G: 271 pages. In total: 1471 pages!
NIST NCSTAR 1-6: 338 pages. N.N. 1-6A: 123 pages (130 pages appendicies). N.N. 1-6B: 107 pages. N.N. 1-6C: 203 pages. N.N. 1-6D: 331 pages. In total: 1102 pages!
NIST NCSTAR 1-7: 171 pages. N.N. 1-7A: 29 pages. N.N. 1-7B: 21 pages. In total: 221
NIST NCSTAR 1-8: 179 pages (12 appendicies!).
On the 20th of November 2008 came the final reports on WTC 7. The reports were NIST NCSTAR 1A (130 pages), NIST NCSTAR 1-9 (731 pages) and NIST NCSTAR 1-9A (121 pages), This gives a total of 982 pages.
Can see a list of all the NIST final reports here[same as above]. To see all NIST's publications about the WTC disaster, can go to this link. To see what the goals and objectives with NIST's investigation, go here.