Why America Slept: The Failure to Prevent 9/11 : by Gerald Posner.

It ought to be interesting to read more on the subject - there was Moore's Fahrenheit 911 (film and book), giving details about various factors of the whole event pointing to suspicious circumstances, to say the very least; and then there was an information channel documentary dramatised with actors to tell the story of how Ahamadshah Massoud, the Lion of Panjshir who had been fighting the Taliban, had warned US and asked for help. He knew he would be assasinated by them and had said, when this does take place, it would be a matter of days until a major attack on US takes place. He was blown up on september 9th, and barely two days later came the attack on US.