False prophets are two a penny in North London - and two a yen in Japan, which for decades has endured "the rush hour of the gods". The falsest was Shoko Asahara, a cult leader who believed that the path to spiritual salvation lay in pumping poison gas into the Tokyo underground system. The 12 commuters dead and the 5,500 injured might have had their theological doubts.
It is not much consolation, but the atrocities of Asahara's killers could have been very much worse. For a start, the sarin gas they used was only 30 per cent pure. They had also considered hydrogen cyanide, as used in Auschwitz, and went shopping in Zaire for the Ebola virus. They tried to purchase second-hand tanks and MiG fighters. They were also toying with the idea of nuclear devices and satellite launchers. Finally, they were working on death rays. They made David Koresh from Waco look like a moderate. Not bad for a cult that purported to be non-violent.
Yet, as David E Kaplan and Andrew Marshall demonstrate, the subway murders were only one part of a very bizarre history. Shoko Asahara was a drifter, mentally and geographically, and a conman who conned himself, until he founded the Aum (ie "Om", the sacred word denoting three Hindu gods): the Association of Mountain Wizards. The "guru from hell" soon had his deluded disciples drinking tea made from his hair and - an acquired taste - his blood. The poor fools wore on their heads a device which gave tiny electric shocks to synchronize their brainwaves (such as they were) with those of their robed leader. In return, they gave him everything.
His HQ at the foot of Mount Fuji might just as well have had a notice over the entrance proclaiming, "You don't have to be mad to worship here, but it helps". The inmates were part of a multi-million dollar empire of armament factories with offices in six countries. The set-up was like something from an early Avengers script - but even more improbable. It wasn't exactly an underground movement (except for its gas attacks): Aum was quoted on the Japanese Stock Exchange and put up candidates for Parliament. Yet the authorities closed their eyes to its activities.
One of the cult's early murder victims was a lawyer who - quite a clue, this - represented parents trying to extract their children from Aum's clutches. Another clue was an Aum badge dropped at the scene of the crime. It was a year before Honourable Mr Plod turned up at the suspects' premises. During later litigation, cultists tried to kill the judges but poisoned the neighbours instead. Police swooped on a man they accused of accidentally making sarin while mixing a herbicide.
After Aum had been widely fingered for the Tokyo gassing, the police got round to staking out a Rolls Royce believed to belong to Asahara; but when it was driven away with a robed man inside, they lost it. Finally they arrested 100 cultists - for offences such as altering a greenhouse without permission. Their sole demonstration of any powers of detection came when they followed an Aum disciple who was carrying melons, the guru's favourite dessert. Clasping state-of-the art canaries to alert them to the presence of gas, they found a secret room where the mad conman was practising his lotus position.
Despite the appalling subject matter, the authors do not avoid its black humour. Their enthralling book has the odd gap: a rehearsal for the gas attack is mentioned but then forgotten. Occasionally you wonder exactly how accurate their account of a conversation between cultists can be; but even if they had made up half of the book, the contents of the other half would still set your mind reeling like a dose of nerve gas.
The wise, final chapter points out the particular dangers of religious zealots: mad Islamic warriors, Messianic Jews, deranged anti-Semites and crazed Christians. Political terrorists are quite prepared to cause deaths, but on the whole they'd like people to take note - which they can't do if they're dead. Cults like Aum believe the end of the world is coming soon anyway. Why not nudge Doomsday a bit nearer?