Before Glenn Greenwald appeared on Newsnight last October to argue the case for the Snowden revelations on a link from Brazil, the presenter that evening, Kirsty Wark, popped into the green room to have a word with the other guests on the show, one of whom was Pauline Neville-Jones, formerly chair of the Joint Intelligence Committee. The interview, she apparently told them, would show that Greenwald was just "a campaigner and an activist", a phrase she later used disparagingly on air.

And so the BBC went after the man, not the story. However, on this occasion, the man held his own rather well, roasting Wark and Neville-Jones with remorseless trial lawyer logic, making them look ill-prepared and silly in the process. At the time, I remember thinking that Edward Snowden had chosen exactly the right person for the job of chief advocate – a smart, unyielding, fundamentalist liberal outsider.

Some of these characteristics made me wonder if his account of the Snowden affair would be one long harangue, but No Place to Hide is clearly written and compelling. Though I have been writing about the war on liberty for nearly a decade, I found that reacquainting myself with the details of surveillance and intrusion by America's NSA and Britain's GCHQ was simply shocking. As the stories rolled out last year, there was almost too much to absorb – from Prism, the program used by the NSA to access, among others, Google, Microsoft and Apple servers, to the UK's Tempora, which taps fibre optic cables and draws up web and telephone traffic; from the secret collaboration of the web and phone giants to the subversion of internet encryption and spying on ordinary people's political activities, their medical history, their friends and intimate relations and all their activities online. I published a dystopian novel in 2009 that featured a similarly intrusive program, which I named DEEPTRUTH, and let me tell you, I didn't predict half of it.

Greenwald's book is a tough read if you find these things disturbing. The insouciance and dishonesty of politicians – some of whom in the UK last week called for increased access to our data – as well as the muted reaction of the established media last year do not augur well for the future of nations that currently regard themselves as free. Democracy and liberty are not synonyms and what Greenwald's book reminds us is that we may well end up as a series of hollowed-out, faux democracies, where the freedoms that we grew up with vanish almost unnoticed, like the extinction of a species of migrant bird.

He writes: "A citizenry that is aware of always being watched quickly becomes a compliant and fearful one", as well as one that is far less likely to express legitimate dissent, of course. The irony of Snowden's actions is that he may have hastened the chill. There are now legitimate things that many of us will never express in private, unencrypted emails or look up on the web because of surveillance.

I read No Place to Hide wondering how we let the spies probe our lives with such inadequate controls, and how on earth we fell for the propaganda that this massive apparatus was there to protect, not control, us. Greenwald quotes Eric Schmidt, the former CEO of Google, saying: "If you have something you don't want people to know about, maybe you shouldn't be doing it in the first place" – and later amusingly catalogues the lengths to which Silicon Valley bosses "who devalued our privacy" have gone to protect their own.

When speaking in public, he often takes on those who say they do not believe that privacy is the core condition of freedom by asking for their private information – passwords, salaries, etc. I have used the same trick. No one ever raises a hand.

The book is organised in three sections, starting with the story of how Greenwald was contacted by Snowden, Greenwald's flight to Hong Kong with film-maker Laura Poitras and their meeting with Snowden, whose bravery and clarity of purpose Greenwald rightly praises. There follows a useful section describing the main revelations, using the original NSA/GCHQ documents, and a third that deals with Greenwald's views on the established media and privacy. It would have been good to have a chart or timeline of the major revelations as well as a proper index. And I did feel the argument lost momentum in the middle, but on the whole this is a vigorously executed and important book.

One of the depressing parts of last summer in Britain was the failure of the quality press and the broadcasting media to react to Snowden and Greenwald is rightly contemptuous of the journalists on both sides of the Atlantic who act as proxies for authority – better an activist journalist than a lackey anytime. But let me just say I think the book does a disservice to my colleagues at the Guardian, which after all is established media. The author tips his hat occasionally but does not really acknowledge the importance of the seasoned reporter Ewen MacAskill's work in Hong Kong, or the team that assembled to sift the documents, decode their inner secrets, prioritise information, gain reaction, shape the stories and provide analysis.

It was one of the most impressive journalistic operations I have ever seen and without it Glenn Greenwald would have floundered and, indeed, have been dismissed more easily as an activist journalist. He has done a great job of exposition and advocacy and for that he should be praised, but credit should be shared.