Reza Aslan was born in Iran, and his parents fled to America with him and his younger sister in 1979, during the revolution. He's a scholar of Islam and its history. When Aslan originally published this book in 2005, it was in response to the growing Islamophobia in the United States and the western world. He wanted to show that Muslims are no different than any other residents on this planet, and that, in the US and other (theoretically) secular western democracies, they are as deserving of religious freedom as Christians, Jews, Buddhists, Hindus, Jains, Sikhs, atheists, and everyone else.
The book that resulted does this very well. He begins with the Arab tribes in what is now Saudi Arabia, where Mohammed lived, and he describes Arab polytheism and their tribal traditions. The origin of Islam that he describes, when Mohammed moved to Medina (then called Yathrib), is one of equality for all.
Aslan spends a good half of the book on Mohammed, his life, and the internecine, often literal, warfare that occurred after his death. He also describes the two main minority sects, Shi'ism and Sufism, each in their own chapter. Then he skips forward to the mid-1800s, when Muslims yearned to throw off the yoke of colonialism in India and Egypt, touching on the effects colonialism had on Islam and its evolution, including the beginnings of the Taliban.
There's a chapter set in the Islamic Republic of Iran, beginning with a description of his trip back to Tehran as an adult after the travel ban was lifted, which leads into a reminiscence of his family's run, hand gripped firmly in hand, through the airport to catch a plane out.
This same chapter ends in India, with the British partitioning of it into Pakistan and India. He says that pluralism and secularization, not secularism, are the key to democracy in the Muslim world, declaring
Finally, neither human rights nor pluralism is the result of secularization, they are its root cause, meaning that any democratic society--Islamic or otherwise--dedicated to the principles of pluralism and human rights must dedicate itself to following the unavoidable path toward political secularization.
Because, in Islam, only the Prophet held both secular and religious authority, and he is no longer here, so the leaders in an Islamic democracy can only be in charge of civil things (like, for example, traffic laws, business regulations, etc).
The final chapter is dedicated to the Islamic reformation. Aslan compares the internet age to Gutenberg's printing press and Luther's translation of the Bible from Latin into German. (In an echo of this concept, The Economist wrote how Martin Luther went viral.) He discusses the various movements in Islam right now and what some of them could result in.
He glosses over the Crusades, unfortunately, and any chapter could easily be twice as long. He gives an extensive bibliography and very detailed end notes, which someone who wants more detail can turn to.
It's very well-written, not dry or tedious, but still with a turn toward the academic at times. It's a very accessible history of Islam, and I highly recommend it.