My reading of the 9/11 Commission report has dropped off significantly after only a few days. It is very good on background and it reminded me of various details that I'd forgotten or hadn't heard about in some time.

If you really want to delve into the 9/11 attacks, and the events in the decades leading up to the event, read through the Center for Cooperative Research's 9/11 Timeline. There is a ton of information there that has been compiled from many many sources.

Use the menu on the right side to navigate the various portions of the project. It's compelling stuff which is why I wasted the better part of a Sunday a few weeks ago going through the seemingly infinite amount of content.