Islamic State: The Digital Caliphate by Abdel Bari Atwan London: Saqi, 256 pp., £16.99 (to be published by University of California Press in September)

In November 2001, two months after the al-Qaeda attacks on the World Trade Center and the Pentagon, James Buchan, a novelist and a former Middle East correspondent, published an article in the London Guardian in which he imagined the triumphant entry into Mecca of Osama bin Laden, the world’s most wanted terrorist:

It was no ordinary evening, but possibly the holiest in the holiest month of Islam, the so-called Lailat al-Qadr, or the Night of Power, on which, according to the Koran, God’s revelation was sent down to the Prophet Mohammed…. More than 50,000 people had gathered on the hot pavement of the mosque enclosure and in the streets outside to pass the evening in prayer. Millions of others were watching on a live television broadcast at home.

As Sheikh Abdul Rahman, famous all over the Islamic world for the beauty of his voice, mounted the pulpit, a hand reached up and tugged at his robe. There was a commotion, and in the place of the Imam stood a tall man, unarmed and dressed in the white cloth of the pilgrim…, and recognisable from a million television screens: Osama bin Laden, flanked by his lieutenants….

Armed young men appeared from the crowd and could be seen padlocking the gates, and taking up firing positions in the galleries.

So began the insurrection that was to overturn the kingdom of Saudi Arabia….

While the details in Buchan’s fantasy describing “the west’s worst nightmare” have changed, the scenario he outlined appears more plausible today than it did fourteen years ago. Bin Laden is dead, thanks to the action of US Navy SEALs in May 2011, but as Abdel Bari Atwan explains in Islamic State: The Digital Caliphate, Ayman al-Zawahiri, bin Laden’s official successor as leader of “al-Qa‘ida central,” looks increasingly irrelevant. Bin Laden’s true successor is Abu Bakr al-Baghdadi, the shadowy caliph of ISIS, the so-called Islamic State. As “Commander of the Faithful” in that nascent state he poses a far more formidable threat to the West and to Middle Eastern regimes—including the Saudi kingdom—that are sustained by Western arms than bin Laden did from his Afghan cave or hideout in Pakistan.

One of the primary forces driving this transformation, according to Atwan, is the digital expertise demonstrated by the ISIS operatives, who have a commanding presence in social media. A second is that ISIS controls a swath of territory almost as large as Britain, lying between eastern Syria and western Iraq. As Jürgen Todenhöfer, who spent ten days in ISIS-controlled areas in both Iraq and Syria, stated categorically in January: “We have to understand that ISIS is a country now.”

In his book, based on visits to the Turkish-Syrian border, online interviews with jihadists, and the access to leaders…