It’s tempting to think of Tony Blair’s career, and his leadership of the Labour party in particular, not so much as a journey than as some kind of manic rollercoaster ride. Not the wimpy ones for the kids but the high-octane, stomach-churning, get-me-off-this-thing variety. Not for the faint-hearted but if you’ve got the balls (one of Blair’s favourite terms of approbation), then buckle up and hold on tight.

Except, of course, that rollercoasters always bring you back to where you started in the end. But Blair, like him or loathe him (there are few undecideds remaining), left the country and the party in a very different place. British politics remains in his shadow, just as Margaret Thatcher’s legacy continued to define the debate until Blair himself broke with it at the end of his first term. David Cameron shows little appetite for breaking the new consensus established by Blair in so many critical areas. But A Journey repeatedly draws a distinction between those who pay lip service to the values and prescriptions that Blair defined as New Labour and those who really ‘get it’. Cameron doesn’t get it, according to his criteria. Will Labour’s new leader?

That is for the future, and the postscript to this book offers some typically uncompromising suggestions for how to address the immediate challenges that have been wrongly characterised as endorsing the coalition’s agenda. Blair is usually more comfortable talking about ‘the future not the past’. Another mistake people made about him, incidentally, was to think that his pithy slogans were devoid of meaning, although to be honest that one very nearly was.

The future is about new challenges, hope and opportunity. The past is too often about the mistakes, regrets and betrayals that go along with the achievements. Blair is far from the only politician who would prefer not to dwell on those. And yet that is one of the many ways in which A Journey is such an unusual and refreshing memoir.

His book is as unpredictable and daring as his leadership was. Progress readers probably need less persuasion than most to approach A Journey without prejudice. Those who loathe Blair with a vengeance, principally because of Iraq, will find little to change their minds. Those who think he was schmaltzy, insincere and just plain annoying will probably find much here to confirm them in that view. It’s certainly the first prime ministerial autobiography to be peppered with observations like, ‘Wow, I was really freaked out’. But for those who are genuinely interested to discover why Blair did what he did and said what he said, then it’s all here. Well, most of it.

There are some obvious omissions. Let’s take one example, Rupert Murdoch. Margaret Thatcher didn’t mention him once in two volumes of memoirs despite the importance of their relationship. Murdoch gets five references in the index to A Journey so that’s progress of a sort. But there’s very little to explain the frequency of their contacts and the complexity of Murdoch’s influence on policy. Perhaps that’s not surprising. Blair resisted all efforts to use the Freedom of Information Act to reveal how often they met and what they discussed. And we now know what he thought of FOI: ‘I quake at the imbecility of it.’

For the most part, however, Blair is wonderfully frank about policies, people and events. Gordon Brown is not the only colleague who must wish he’d been more circumspect. In a surprising aside on politicians and sex Blair talks about the ‘free bird instincts’ that make people who are normally constrained by caution and self-control want to be released and feel free for once. He exercises that freedom here in a way that makes the book hugely entertaining and often very funny indeed.

His description of Millennium eve, the chaos at the Dome, and his premonition that the Queen was about to be killed by a free-falling acrobat with no safety net is priceless. I learnt things that I didn’t know – or perhaps only suspected – at the time. When he was relentlessly driving his staff to extol the virtues of the Dome, it’s probably just as well that we didn’t know he was barely convinced himself and ‘if it had consisted of a man slapping everyone around the face with a wet fish, we would have stoutly held it to be a work of genius’.

When he was so foolishly expending valuable political capital trying to prevent Ken Livingstone become mayor of London, would people have tried so hard to do his bidding if they’d known he thought that Steptoe and Son’s horse stood a better chance of winning than Labour’s candidate, Frank Dobson?

On the much bigger issues of public service reform, Northern Ireland, Kosovo and Iraq, Blair eschews such flippancy to give a detailed and thoughtful account of what happened and why. It has the honesty of a man who seems no longer to care what people think of him. As he says on Iraq, he is trying ‘not to persuade’ but only to make those who ‘adhere to the conventional wisdom at least pause and reflect’. If they do so they may not change their minds, but they will have a better understanding of what was going on in his.