Ed Husain is a busy man. He is working on a PhD, and his book The Islamist has generated a huge amount of copy and follow-up work. Earlier this year, going home on the train after a tranche of interviews, he got a call from an old Muslim friend.

‘Salam Alaikum!’ I said. ‘How are you?’ My friend was in no mood for niceties. He was blunt and sharp as he warned me to stay away from a particular London mosque: ‘You won’t escape safely. Do you hear?’

I was perplexed. All week Muslim ‘community leaders’ had been rapping me on the knuckles for attacking, in my book, those who managed the mosque and its various octopus-like arms. ‘They’ve changed, Ed,’ was an argument I heard a lot. ‘They’re not connected to extremism or violence.’ So how was it that peace-loving Islamists at this mosque would want to attack me?

How indeed? After all, Husain was a convinced Islamist for many years. As a teenager he grew bored with his family’s traditional, community-based Islam and became involved with a network of hardcore fundamentalist groups. The first half of the book deals with Husain’s years in Jamat-e-Islami and Hizb ut-Tahrir. The youthful Husain has dozens of aspiring jihadis under him and is practically running his college from the bottom up. He holds rigged debates and disseminates propaganda against women’s rights, gay rights, the Jewish people, nonbelievers, democracy and secularism.

The Islamist is blurbed as ‘what politicians and Muslim ‘community leaders’ do not want you to know’ and indeed it is scary to recognise names from Husain’s past who are now respected voices in the government and media. Inayat Bungawala, a future assistant secretary-general of the Muslim Council of Britain, takes Husain to a ‘family gathering’ where they cheerfully nod along to the mutrabbi’s monologue on ‘destruction of the state of Israel and the return of Muslim control of the Holy Land.’ Azzam Tamimi, a columnist for the Guardian’s ‘Comment is Free’ as well as a supporter of Hamas, also appears, as do several other reactionaries who are now leading members of George Galloway’s pseudo-left Respect Party.

When a young Christian boy is murdered over an argument about whose turn it is to use the college pool table, Husain begins a long, painful process of disengagement. His views become more nuanced and reasonable – so it’s a shock to note that his initial reaction to the September 11 attacks is one of satisfaction. He’s not alone. Many of his Muslim friends are drawn into the fevered swamp of 9/11 conspiracy theories. There is a popular rumour that ‘over 2,000 Jewish people had been tipped off by the Israeli embassy not to attend work on that day.’ Husain could have added that such poisonous thinking is not unique to Muslims; I have met Western ‘leftists’ who believe that same sinister rumour.

In the last third of this brave book, Husain travels to Saudi Arabia and Syria where he works as a teacher for the British Council. This part of his story is striking, because of its spiritual and political insights and because Husain for the first time experiences society in the Islamic state that he once fought for. He concludes that life under theocracy is miserable, and that Muslims have more freedom of religion under decadent, secular Britain than in a faith-based regime. He also discovers that under theocracy, some believers are more equal than others:

The hallmark of a civilisation, I believe, is how it treats its minorities. My day in Karantina, a perversion of the word ‘quarantine’, was one of the worst of my life. Thousands of people who had been living in Saudi Arabia for years, but without passports, had been deemed ‘illegal’ by the government and, quite literally, abandoned under a flyover.

A non-Saudi black student I had met at the British Council accompanied me. ‘Last week a woman gave birth here,’ he said, pointing at a ramshackle cardboard shanty. Disturbed, I now realised that the materials I had seen these women carrying were not always for sale, but for shelter. While rich Saudis zoomed over the flyover in their fast cars, others rotted in the sun below them.

This book is an argument against Islamism but also an argument for Islam. It’s also a great crash course in the history and variants of the religion. Husain makes a convincing case for Islam as a religion of peace, distinct from Islamism the jihadist political ideology. He points out the fanatics’ ignorance of even basic Muslim practices, and quotes parts of the Koran that advocate tolerance and love. Yet Husain’s moderate Islam, while much better than fundamentalism, still has problems. His embrace of Sufi mysticism, with its emphasis on the surrender of the individual self, reflects an unacknowledged totalitarianism in Eastern religions; the soul swallowed up by an abstract nothingness.

In his final chapter Husain succumbs to a nasty purist critique of the West:

Anti-social behaviour in our cities, high rates of abortion, alcohol abuse and drug addiction are abhorrent to all right-thinking people, not just Muslims…When the centre of social life in modern Britain is the local pub, where do Muslims and others fit in? (Emphasis mine).

In these words there is an echo of Sayyid Qutb at the edge of the dance. If religion is to have any relevance at all in the twenty-first century, it has to reach some sort of acceptance of the right to pursue pleasure. Husain quotes the Islamic poet Rumi: ‘the religion of Love transcends all other religions: for lovers, the only religion and belief is God.’ I agree with the first part.

But overall, this is an essential book by an intelligent and courageous writer. Too many people think all Muslims are Islamists, because the only voice that British Muslims have is through reactionary and unelected community leaders. Now, with groups like British Muslims for Secular Democracy and the New Generation Network, the other Muslims are finally getting some representation. They can take comfort from the words of Husain: ‘Talk of execution will not cow me; I will carry on.’