Those 22 days packed a lot in: goodbye Gordon, hello David, hello Nick  and hello and goodbye David Laws, the shortest-lasting chief secretary to the Treasury since records began. Count one more expenses scalp for the Telegraph, but look on the positive side, too. Laws has had plenty of time to write this Lib Dem insider's first rough draft of coalition history since 29 May. Maybe his prose is penny plain, but the story he has to tell is full of rich detail  and comes with a vital five months' worth of perspective.

We knew the basic outline of Tory negotiations already, perhaps: a clear-headed David Cameron deciding what he wanted, making sure that William Hague and the Tory team addressed Liberal Democrat "red line" issues  and keeping back channels to Nick Clegg open wide. But the thoroughness of Liberal preparations long before any votes were cast is a revelation of unexpectedly hard-headed professionalism  just as the shambles of Labour's non-fight for survival passes all previous understanding.

Months before May's election a full-blown coalition agreement lay smack in the middle of the Liberals' sandbox. Chris Huhne  one of the party's bargaining quartet  hymned its advantages from day one. But Huhne was thinking of a Lab-Lib pact, and so were most of the party. Paddy Ashdown, still a big cheese at the back of the dairy, thought his moment of heart's desire had come. Ming Campbell couldn't stomach any other sort of deal; and nor could the vast majority of MPs and grandees.

Of course the election result itself gave such dreams a nightmarish tinge (who wants to rely on the DUP when things get tough?), but this was still the most favoured show in town. A "coalition of losers", however rickety, was still the bookies' best bet  until Labour blew it. Brown wanted to hang on, and told Clegg so at inordinate length. But Brown was the problem, not the solution. He couldn't be prime minister in any successor administration, but neither, it seemed, could anyone else. David Laws, Danny Alexander, Andrew Stunell and Huhne sat through two long negotiating sessions, convinced that Peter Mandelson and Andrew Adonis wanted a deal, but bemused as to where Harriet Harman and the two Eds stood.

Could they deliver on voting reform, the reddest of red lines? Ed Balls wasn't sure about that (even though it had been in Labour's manifesto). Didn't they see that a marriage this flaky would send the markets into a spin unless £6bn or so in cuts was offered upfront by a June budget? "This would be very bad for credibility, because we couldn't do it," said senior Ed. "Oh no, we cannot go further than our existing agreements with the unions," said junior-but-about-to-be-senior Ed.

So, in the end, there was only one partner left to dance with. In one sense, Labour did the coalition in general, and the Liberals in particular, a great good turn by making an alliance with Cameron inevitable. Clegg's rambunctious party couldn't cut up rough, because Labour had offered no alternative.

If you want to know why Labour lost Downing Street, don't ask the Conservatives or Lib Dems. Ask why nobody in a fading government, expecting defeat, had got a grip; ask why nothing could be done. And ask, too, as "blank slates" are produced for a new Labour generation to write on, whether the old generation just threw up its hands and gave it all away.

David Laws has copious notes of interminable meetings to rely on, which means his account has the ring of authenticity. It's a brisk, rewarding read that makes you feel more participant than spectator. It also catches the milling chaos of the time, the imperative that a deal be done in  yes!  the national interest, because the cabinet secretary and governor of the Bank of England were dancing jigs of anxiety just off stage.

Policies? They are what politicians always say are important, of course. But tax cuts for the poor and premiums for deprived pupils aside, they don't take up many pages here. Can the Liberals decide not to join the euro this time round, please? They can grin with relief as they do so.

If you want policies without the politicking, then a full-dress explanation of the "big society" by Jesse Norman, one of conservatism's most fertile gurus, is a much more nourishing read  except that you still can't make soundbites from it. Hobbes, Descartes and de Tocqueville get their mentions. Michael Oakeshott is a hero. We're way beyond Cameron's caring/sharing nostrums, and delving deeper in search of community values, personal freedoms and related heavy-duty stuff. It's a fluent but somehow elusive tract: you understand why full disclosure of government spending fits the bill; but you can't remotely understand how proper proportional representation doesn't. Maybe Laws could wrestle with that in his next book  assuming he's still got free time.

 Peter Preston's The 51st State is published by Penguin.

 This is a preview from tomorrow's Guardian Review.

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