This self-serving memoir confirms that George W Bush is a moronic war-monger who can't think straight, can't string two words together and spent his presidency looking for countries to invade, oil to snatch and ways to make the world a more dangerous place.

There, I've said it, and the conventional wisdom chatterati will nod amen to that. The problem is that none of the above is true. Cue avalanche of Guardian Online vitriol.

You see, in Guardianland, as in other parts of the world, one is not supposed to think anything but ill of Bush. "Is he as stupid as he looks?" is up there alongside "did you invent the phrase the 'People's Princess'", "do you regret the dossier?" and "is Malcolm Tucker based on you?" as frequently asked questions at Q&A sessions I do.

My answer to the first is that you don't get to be US president  twice  by being stupid; that he is more reflective and self-analytical than the public image suggests  a trait confirmed by his book; that September 11 changed the world in the eyes of most Americans; and that I do not buy the idea that he was hellbent on war in Iraq  also confirmed by the book, and in particular by the letters to his father and daughters. They are the letters, and this is the account, of someone who tried to avoid war, but could no longer ignore Saddam's defiance, or the view of every intelligence agency in the world that Iraq had WMD, a threat that could be parked pre-September 11, but not after it. And surely he has a point when he says: "If I wanted to mislead the country into war why would I pick an allegation that was certain to be disproven publicly shortly after we invaded the country?"

Doubtless the Bush-haters will assume he wrote the letters to his family as a form of prewar spin planning that could be trotted out postwar when it all went wrong. All I say is: read them. You would be hard pressed, on a fair reading, to say the chapters on Iraq show a "rush to war".

The reactions Bush provokes sometimes make me think the public don't mean it when they say they want politicians who speak as they find. I remember a dinner in the White House where Bush said he had pleaded with German chancellor Gerhard Schröder not to fan anti-Americanism in his re-election campaign. Schröder said he wouldn't. Then, struggling in the polls, he did. Schröder fares badly in this book.

Yasser Arafat fares worse, not least over corruption. I remember Bush telling us he had warned the PLO leader that if he lied to him about involvement in terrorism, he would not get back in the White House. "Arafat had lied to me," he writes. "I never trusted him again. In fact, I never spoke to him again." Obstinacy, stupidity, or a politician saying what he would do, and then doing it  that trait we are supposed to want in our leaders?

The Bush-haters will say this is just the usual thing of American presidents doing Israel's bidding. But as he points out proudly, he was the first president publicly to call for a Palestinian state as a matter of US policy, against the wishes of the powerful trio of Dick Cheney, Colin Powell and Donald Rumsfeld (I was surprised to learn Rumsfeld's appointment was Condoleezza Rice's idea, by the way).

Rather than write a traditional memoir, Bush has taken key decisions in his life and career and explained why he made them. Having discussed drink problems with him, I'm not surprised the first chapter is "Quitting", or that God appears on page 2, and regularly thereafter. Bush certainly does God.

For a British audience, however, the dramatic accounts of his first, judge-settled election win, September 11, the war in Afghanistan and the war in Iraq are likely to be the most relevant chapters, and they go in some depth into how he handled each one. But I found myself more interested than I expected to be in the "Stem Cells" chapter, as he explains how he came to his compromise position on research, seeking to reconcile his faith, his politics and the enormous different pressures he was coming under. Likewise his chapter on hurricane Katrina is not a bad contribution to the body of work on crisis management.

On Katrina as elsewhere (including on Iraq, on domestic policy and on his habit of shooting from the lip), he is not shy in admitting mistakes or in expressing frustrations at constantly being described as the most powerful man on the planet, yet often feeling powerless. Similar frustrations spill out in his inability to hold together the foreign policy team, with the Pentagon and the State Department regularly at odds. This theme emerges most dramatically perhaps when the secret service refuses to allow him to go to Washington after the September 11 attacks. "I had the most powerful job in the world, yet I felt powerless to help them [the American people]."

It is interesting, too, that Aids and Africa should figure in his top dozen decision points, and that he should describe the lowest moment of his presidency not as the failure to find WMD, or the writing of several thousand letters to the families of fallen soldiers, but the accusations of racism in his handling of Katrina.

As with virtually every post-Lincoln presidential memoir, Abraham Lincoln weaves his way through the pages. His father and Ronald Reagan are also major influences, as are Roosevelt and Truman. Perhaps wistfully, Bush points out that Truman left office deeply unpopular, with his ratings in the 20s, yet is today seen as one of the greats. Bush is unlikely ever to get near the Lincoln league. But a fair-minded assessment of his book should at least allow people a better and deeper understanding of him, the decisions he faced, and how he came to make them. The problem is that balance has for now gone out of the assessment. Tucked away at the end of chapter 6 is the observation that for seven and a half years after 9/11, America was not attacked again. Bush sees it as his "most meaningful accomplishment". He did not ask for September 11 to define his presidency. But it did.

Alastair Campbell was Tony Blair's director of communications and strategy. The second volume of his diaries, Power and the People, is published in January.

 This is a preview from tomorrow's Guardian Review.

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