Standing in line for his photographic keepsake was the Washington Post reporter and author, Bob Woodward, whose investigations into the Watergate scandal had played a central role in bringing down President Richard Nixon.

When Woodward reached the front, the president congratulated him on the sales of his book, Bush at War, which covered the period from September 11 to the fall of Kabul.

"Top of the charts," Mr Bush said. "Are you going to do another book?"

"Maybe it will be called More Bush at War," Woodward replied.

In fact, his latest book, Plan of Attack, detailing decision-making in Bush's inner sanctum in the run-up to the Iraq war, could have been entitled just that. Its release this week had much the same effect within political circles as JK Rowling has in the playground.

The book tells readers that Mr Bush gave Tony Blair the option of not sending troops ("I appreciate it ... but I'm with you to the very end," Mr Blair said); that Saudi Arabia's Prince Bandar saw the confidential war plans before US secretary of state, Colin Powell; and that the Bush administration diverted money intended to fight terrorism to prepare for an Iraq invasion. Revelations from Bush at War have featured prominently in evidence at the 9/11 commission examining how and whether the White House could have prevented the terrorist attacks on New York and Washington.

Plan of Attack is the latest of several books to have serious repercussions. In Against All Enemies, Richard Clarke, the former counter-terrorism tsar, sparked a firestorm with his allegations that the White House had mishandled the threat of al-Qaida because it was obsessed with Iraq. Earlier this year, the former treasury secretary Paul O'Neill's account of a cabal of ideologues leading an uncurious, unintelligent president also made headlines.

But while Woodward might not be unique, his book is unrivalled in the access he has gained with all the main players. He had two interviews with the president, as well as with Colin Powell, the national security adviser, Condoleezza Rice, the secretary of defence, Donald Rumsfeld and the head of the CIA, George Tenet.

There are two main explanations for Woodward's access. First, he is not just a chronicler of events but a player. When the White House heard that two Washington Post reporters were planning to write a story of a possible nuclear bomb threat, a CIA official called Woodward hours before it was due to run and asked him to get it pulled because it would upset the Pakistani regime. The official only then called the Washington Post's executive editor, Len Downie, who delayed publication for several days.

Second, the book is not a critical account of the Bush administration. Although Woodward says he cross-checks each protagonist's account against others, there are few challenges to what they say.

Asked whether he wanted a war, Mr Rumsfeld - one of the leading hawks - says: "Oh goodness, no. No one with any sense wants conflict." The response goes unchallenged.

When Mr Bush is presented with the plan for the surprise attack to try to kill Saddam Hussein and his sons that started the war, Woodward conveys that the president's primary concern was for Saddam's family. Hours later, according to the reporter, "Bush was still worrying about the women and children". Little wonder, despite the book's accounts of insider fighting, that the administration has not tried to discredit Woodward, as it did Mr O'Neill and Mr Clarke, but declared itself happy with the book.

For all that, two key insights about the administration emerge. The first is that self-deception reigns within Mr Bush's inner circle. Once, when asked how he gets his information, the president replied: "The best way to get the news is from objective sources. And the most objective sources I have are people on my staff."

The book exposes a circle of believers - with the notable exception of Mr Powell - who tell the president what he wants to hear rather than what he needs to know.

After an unimpressive slideshow about the evidence for weapons of mass destruction in Iraq, Mr Bush turned to the CIA chief, Mr Tenet, and says. "I've been told all this intelligence about having WMD, and this is the best we've got?"

"It's a slam-dunk case," Mr Tenet replied.

"George, how confident are you?"

"Don't worry, it's a slam dunk!"

Iraqi dissidents are ushered into the Oval Office to tell Mr Bush that troops will be greeted "with flowers and sweets". In a personal intelligence estimate, the vice-president Dick Cheney, said: "Simply stated, there is no doubt that Saddam Hussein now has weapons of mass destruction."

The slope from assumption to presumption to pre-emption is travelled in a manner that highlights the second insight, namely the deceit that emanated from the White House. From the first page - where Mr Bush is described asking Mr Rumsfeld on November 21 2001: "What kind of war plan do you have for Iraq?" - the reader is left in no doubt that the dominant forces in his administration are determined to bomb Iraq and remove Saddam.

With the plans fully under way in April 2002, the ITN newscaster Sir Trevor McDonald asked Mr Bush whether Saddam was a target for attack. "I have no plans to attack on my desk," Mr Bush said.

In all this, the diplomatic avenues pursued through the UN were little more than a sideshow: a parallel track that the rest of the world followed in good faith. According to Woodward, the day before Iraq was due to let in UN weapons inspectors, Mr Bush told Mr Rumsfeld and the head of US military central command, General Tommy Franks, to "dissociate a big deployment or build-up from what Colin is doing on the diplomatic front ... Don't make it look like I have no choice but to invade."

Given events since the invasion - the resistance, the lack of WMD, the administration's return to the UN looking for help - it is little wonder that the book's epilogue is longer than most of the chapters.

In an exchange that illustrates both the status of the author and the state of mind of his subject, Woodward asks Mr Bush why he has not acknowledged that WMD have yet to be found.

Mr Bush says no one in his entourage has suggested that he make such an acknowledgement, before taking a swipe at Woodward: "But you run in different circles than I do. Much more elite."