“The First Muslim” tells this story with a sort of jaunty immediacy. Bardic competitions are “the sixth-century equivalent of poetry slams.” The section of the Koran known as the Sura of the Morning has “an almost environmentalist approach to the natural world.” Theological ideas and literary tropes are “memes” that can go “viral.” Readers irritated by such straining for a contemporary tone will find it offset by much useful and fascinating context on everything from the economics of the Meccan caravan trade to the pre-Islamic lineage of prophets called hanifs, who promoted monotheism and rejected idolatry.

In the terms it sets itself, “The First Muslim” succeeds. It makes its subject vivid and immediate. It deserves to find readers. However, its terms are those of the popular biography, and this creates a tension the book never quite resolves. Though based on scholarship, it is not a scholarly work. Factual material from eighth- and ninth-century histories is freely mixed with speculation about Muhammad’s motives and emotions intended to allow the reader, in the quasi-therapeutic vocabulary that is the default register of so much mainstream contemporary writing, to “empathize” or better still, “identify with” him. Inevitably, a forest of conditionals surrounds such speculation, as Hazleton tries to intuit what Muhammad “must have felt” or “surely would have” done. “For an adolescent trying to cement a life from the shards of loss and displacement,” we are told, “the monotheistic idea has to have been immensely powerful.” One might equally be justified in saying that animism would have made him feel less alone. Elsewhere we are invited to appreciate “the sheer humanness” of his terrified reaction to the Koranic revelation. Occasionally a novelistic impulse takes over, as in a passage describing a flash flood where “you” “flail and fall” and try to pick yourself up because “the roar of it is on you now.” Has Hazleton been in such a flood? Is she paraphrasing someone else’s account? This is innocent enough as an exercise in style, but it makes one uncertain about the status of more substantial passages.

Muhammad’s transition from humble messenger to political leader, and from peaceful preacher to war leader, forms the substance of the story. The factional struggles, political assassinations, night flights and pitched battles that surround it are reminiscent of the experience of another prophet, the Mormon leader Joseph Smith, as is the role of revelation in exonerating sexual impropriety — in Muhammad’s case to allay suspicions of infidelity surrounding his third wife, Aisha. Despite the orthodox Muslim insistence that Muhammad, while possessed of human failings, is irreproachable, some of his actions are deeply troubling. Even Hazleton finds it hard to put a positive spin on the mass beheading of up to 900 surrendered men of the Jewish Qurayza tribe, losers in one round of the factional battles for control of Medina.

However accurate her book, however laudable her intention to bridge the chasm between believers and unbelievers, Hazleton still has to confront the question of the authenticity of religious revelation. Respect is not the same as belief: her interpretation of “whatever happened up there on Mount Hira” is to stress Muhammad’s “experience” of revelation while sidestepping its objective existence. In various places, she hints that the Koran and the Hadith, like other holy books, have a textual history and that certain events in the life of Muhammad are best considered tropes. A fuller examination of these points would have been fascinating, but it would have forced her to embrace the perilous notion that the Koran, instead of being the revealed word of God, might be a text like any other. In evading such material Hazleton clearly hopes to avoid giving offense, but try as she might, she cannot escape the fact that in our time even a well-meaning and fundamentally decent book such as this can never be innocent, because it cannot stand outside our violent recent history.