Like many recent years, 2013 saw Richard Dawkins tweet a summary judgment about Islam. “All the world’s Muslims have fewer Nobel prizes than Trinity College, Cambridge. They did great things in the Middle Ages, though.” The coarse implication in his first statement is hardly softened by the condescending allusion to the “great things” done by past Muslims. Still, it was only a tweet. Islamic Empires, Justin Marozzi’s new work, is a 464-page elaboration of the same argument, with additional bloodshed and sleaze.

Marozzi opens by quoting a Tunisian friend who is “embarrassed to be an Arab these days”, distressed as he is by the “chaos, fighting, bloodshed, dictatorship, corruption, injustice, unemployment” plaguing the Middle East. The Tunisian certainly has a point, but it’s one that Marozzi misconstrues. Marozzi advises his friend to think back to a time when “for an Arab Muslim, pride in occupying the very summit of the global pecking order, rather than shame and embarrassment at languishing in its nether regions, was the order of the day”. But Arab spring protesters, just like this Tunisian, were complaining about their corrupt rulers and calling for a fairer society, not the restoration of what Marozzi calls a “famed” and “feared” caliphate in order to satisfy their “pride”.

The author offers potted histories of 15 mainly Arab cities across the 15 centuries of Islam. He picks them during their most opulent eras: Baghdad in the ninth century; Cairo in the 12th; Constantinople in the 15th; Isfahan in the 17th; ending with Doha in the 21st. As a journalist, he has visited nearly all the cities he describes, and begins his chapters by speaking to interlocutors often depressed about the state of their country. Then he swiftly whisks us back into a glorious past, emphasising the most lurid tales.

First up is Mecca in the seventh century, the city in which the prophet Muhammad was born and which he eventually conquered. Or did he? Like the historian Tom Holland, Marozzi casts doubt on the traditional account of Islam’s origins, speculating that Mecca might not have been where the religion really began. Going down the sceptical route is fair enough – it’s still a contested issue among academics. But Marozzi’s scepticism is selective. For within a few pages, he is confidently retelling the story of the Prophet condemning to death 700 men from a Jewish tribe that had betrayed him. Does he only trust the sources when there is a juicy story of Muslim violence to tell?

I lost count of the number of beheadings and executions in this book, all told with a grisly relish. Muslim chroniclers are Marozzi’s sources, of course, but like all chroniclers they exaggerate for political reasons or simply to impress the reader; it is unlikely, for example, that the eighth-century Abbasid general Abu Muslim “killed 60,000 people in cold blood”. Then there are the enervating lists of expensive stuff: after his death Harun al-Rashid, the caliph best known from the Arabian Nights, apparently left “4,000 turbans” and “1,000 pieces of the finest porcelain”; a later caliph had “7,000 eunuchs” and “4,000 black pages”. Marozzi has a wide-eyed credulity about such numbers to match that of those literalistic Muslims wedded to every detail of the prophet’s life story.

His intellectual history is equally shaky. Rightly, he nods to Baghdad’s library the House of Wisdom and the translation of Greek texts into Arabic, and to the impressive scientific and philosophical work of al-Khwārizmī and al-Kindi. But he simplifies the narrative to suit modern tastes, pitting “conservative clerics with closed minds” against “the free-wheeling philosophical, religious and scientific discussions” at the Abbasid court. Ignored are the sharia scholars who also contributed to Islamic intellectual culture.

Consider Ahmad ibn Hanbal, founder of one of the four major schools of Sunni thought. He was flogged during the ninth-century mihna or inquisition, which enforced rationalist interpretations of the Qur’an and persecuted traditionalists. The mihna goes unmentioned here, probably because it complicates the book’s cartoon version of the past in which narrow-minded theologians were outsmarted by philosophers at a court where “drinking bouts, lavish feasts, orgies and homosexual liaisons” were commonplace.

Time and again Marozzi treats us to lusty descriptions of “wine-soaked, hashish-perfumed” parties or the sexual prodigiousness of slave girls. Entertaining enough, if that’s your kind of thing; but the licentiousness is made to bear too much historical weight. He thinks living it large is a quintessential marker of an Islamic empire’s “self-confident pluralism”. He rarely stops to think of what life was like for slave girls wrenched from their distant homes, and whether they were quite so keen on this early form of “multiculturalism”.

Gender relations are not examined with any depth here, even though there is much fascinating material outside elite, male-dominated circles. As Yosef Rapaport has shown, middle-class women in medieval Cairo often initiated divorce – many had strict pre-nuptial contracts drawn up under the sharia. But Marozzi is too distracted by the Cordoban princess “who decorated her robes with her own verses celebrating sexual licence, embroidered in gold,” or the tales he hears from a modern Cairene woman about “free-spirited girls fellating in veils”.

A key question – unanswered here because unasked – is what actually connects these disparate times and places? Is there something essentially “Islamic” about violent conquest, louche hedonism and intellectual endeavour? Given that for centuries after the prophet’s death more non-Muslims lived in the caliphate than Muslims, why even label it Islamic? And since these empires were often at war – Fatimids versus Ayyubids, Safavids versus Ottomans – can they be lumped together as one “civilisation” that rises and fades like, in one of Marozzi’s favourite metaphors, a shooting star across the heavens?

Of eighth-century Syria, he writes there was “tolerance and more or less harmonious coexistence” between the religions, drawing a melancholy comparison with today’s horrible sectarian war. But can present and past conflicts be explained by reference to whether Islam is essentially “tolerant” or not, as Marozzi seems to think? Such questions have worried well-known historians such as Marshall Hodgson and more recently Shahab Ahmed and Jack Tannous. Their works are absent from the bibliography.

As Marozzi surveys the ruins of Kabul and Baghdad and wearily shakes his head over a lost golden age, his story’s looming shadow becomes more conspicuous. For who now heads the “global pecking order”? Who invades weaker countries? Who accumulates wealth through technological ingenuity and embraces sexual freedom to the point of decadence? That is a caricature of the west to be sure, but one that Marozzi projects back on to older Islamic empires.

The unspoken message to Muslims? Make your nations great again by becoming more like us. So this is less a book about “Islam’s superiority complex”, as the author puts it, than about the west’s. It says so much that of all the thriving modern cities with large Muslim populations Marozzi could have explored – Delhi or Jakarta or Amman – he prefers to visit Dubai.