There aren't many books on Islam where the Prophet Muhammad and Martin Scorsese appear together. But Jonathan Brown's book is about recounting history, multiple interpretations and making sense of legacies; religious traditions and Hollywood films have these tensions in common. Both want to convey particular stories to a diverse range of audiences, and to convince them of certain metaphysical truths.

Brown's inspiration for the book comes from the New Testament scholar Bart Ehrman's bestselling Misquoting Jesus, a work which looks at the accidental or intentional textual variations of the Bible. Brown explains that his own focus is more on the challenges of interpreting the Prophet's legacy rather than "unveiling Islamic origins". He explores the rich interpretative history of Islam and how the faithful continue to be challenged.

Much of what Brown is really exploring is the status of the sayings or traditions of the Prophet – hadiths. These were compiled in their thousands and form the basis of much of Islamic dogmatic, legal and theological thinking from the earliest times. They are second only to the Koran as a source of authority. But how many of them are reliable, and why do Muslims continue to be guided by them when so many are disputed even rejected by scholars? The book tries to get to the bottom of these debates.

At a time when Islam or the cultural practices of Muslim societies are under a constant spotlight, many scholars of Islam, especially American scholars, are engaged in placing sensitive matters in context. They want to say something credible to their academic peers but also appeal to a more general audience. The book is helpful for the lay reader who wants to understand why what the Prophet said matters in Islam and how his words and actions have been interpreted.

The reader may be surprised to see that, in a similar way to the mutable biblical canon, the Prophet's words form a corpus which has always been subject to scrutiny and controversy. This is partly because there are many opinions of the Prophet's companions which have been deliberately or erroneously attributed to the Prophet himself. While the Koran is regarded as God's revealed word, the vast corpus of the sayings of the prophets is far more controversial and amorphous. This corpus may have canonical status and have been passed down through generations, but there are variations within the hadith collections and many have been declared to be unreliable, even forgeries by Muslim scholars themselves. The scholar of Islam will find a potted history of hadith science and a useful summary of major names and developments including current fatwas (opinions) by notable muftis.

Muhammad's status in Islam is not that of Jesus in Christianity but his standing, words and actions are fundamental to how millions of Sunni Muslims understand their own history and ethical dilemmas. This is not Brown's first book on prophetic traditions so he is very much at home in discussing the science of hadith interpretation as well as its controversial legacies. But the language is not arcane. It tries to weave multiple narratives together including Western approaches to scriptural interpretation as well as aspects of Brown's own more personal journey.

The constant references to past and present thinkers are a major stylistic feature of this book, allowing the reader to appreciate the long history of ethical debates. The content is largely rooted in Islamic thought but it also includes comparisons with Western and Christian thinkers such as St Augustine, Martin Luther and Immanuel Kant. For Brown, it is the 18th-century Mughal modernist Muslim scholar Shah Wali Ullah who epitomises the struggle to reconcile reason with revelation and who has a particular and persistent presence in this book.

Readers who are turned off by this kind of drier historical mapping may find Brown's analysis of contentious scriptural verses more intriguing. These are the debates which have proved difficult for Muslim thinkers but also often comically captured the Western imagination. He takes the reader back and forth in time with a plethora of Islamic references to show how the scholars balanced their desire to maintain the authenticity of Islamic scriptures with the realities of people's lives. Brown encapsulates these tensions under pithy chapter titles, for example: "When scripture can't be true" or "Lying about the Prophet of God". These are then followed by case-like analyses of subjects such as "The Koran and domestic violence" or "Who decides what God means?"

Perhaps the most controversial title is "Sex with little girls" referring to Muhammad's own age of 50 when he married Aisha, who is reported to have been around 10 at the time. Issues of gender injustice such as honour killings, the wife-beating verse and patriarchal attitudes to women's leadership are all present.

Much of what Brown does is to set forth competing interpretations on these themes, often with surprising conclusions. What he doesn't do is position himself on these difficult issues. This is because Western Muslim scholars should have more courage to say what they think is morally right. The book is not just about methodologies; it is also about ethics.

Scripture is lived though the actions of the faithful, which requires wrestling with established opinions and one's own conscience. It demands having a clear voice and not hiding behind others. Muslim scholars in the Islamic world do not have a monopoly on interpreting Islam's rich legacies.