It's in Holland's first chapter where he sets the stage for the book. There are virtually no contemporary sources on the life of Muhammad, and the few that do exist only give the barest hint of the historical existence of what later became the life of the prophet.
But while the bulk of the book is an extraordinary and immensely interesting walk through of late classical times, using recently uncovered facts to make fascinating if reasonable claims, while grippingly bringing this distant and vast ancient history to life, it is a tad disappointing that Holland almost seems afraid in taking a firm stand on his, to Muslim scholars, unorthodox views of both Muhammad and the Quran. Even the chapter that specifically deals with the Quran is called 'more questions than answers', appearing afraid to offend.
Perhaps he likes to leave drawing conclusions to the reader. That said, little reading between the lines is necessary to see the bigger picture. Muhammad, if he existed, came from the middle eastern borders of the late Roman empire, say the area between The Roman empire and Sassanid Persia, but specifically not Arabia. The Quran is likely a product of a later date, the first 'believers' simply being a slightly offbeat Jews, or Christians. Muhammad's tribe, the Quraysh, most likely a term to describe all Arabs.
None of the Hadith, the sayings of the prophet, can be truly attributed to the man, while a large part of the accepted context of the creation of the Quran is, at worst, complete conjecture and, at best, unverifiable. Indeed, it is not at all clear when and where the Quran was actually created and whether, indeed, Muhammad did exist. Holland points out that there are about as many theories on the creation of Islam as there are scholars.
It was only in the fifth or sixth century that the Zoroastrian faith came to be shaped as a separate church. Only then were the founding stories of that faith put to paper, making the religion, which before dovetailed with separate but intertwined state power, into much more of an individual church.
Interestingly, Zoroaster's revelation of the faith is comparable to Muhammad's. Holland paints Islam as a natural successor to Zoroastrianism, with some of the outer appearances of Islam being an implicit continuation of earlier customs. One interesting example being Islam's color green perhaps being modeled on a Parthian identifier, armies clad in green, trying to reestablish control of the Persian throne after the demise of the Sassanid king Peroz, battling the Hephtalites, 'white Huns' coming in from the north eastern steppes.
And there is the obscure prophet Mazdek, who lead what can only be called the first communist revolution in history, striving for an equal distribution of wealth.
Holland makes a connection between the Quran and the Hadith, the collection of sayings attributed to the prophet, with the Jews' desire to anchor their faith during the first few hundred years AD with, besides having the Torah, also writing down, for the first time, the Talmud, the collected interpretations and wisdom passed down from rabbi to rabbi as the perfect accompanying column to the Torah.
It was in the tenth century that a Muslim scholar established what became an orthodoxy for some 900 years, that there were seven, equally valid, readings of the Quran. The modern view that there is only one single text dates from 1924, following the publication in Cairo of an edition of the Quran that went on to become the global standard.
The Quran mentions three peoples of the book, which need to be treated with a tad more respect than the general collection of unbelievers. Besides Jews and Christians, the third are the Sabaens, the founders of Erhiopia, named for queen Sheba who, according to legend, was tricked by king Solomon into having sex and returned to Ethiopia with the father of all subsequent Ethiopian kings in her belly.
The Sabaens, as Ethiopians, ended up being one of the first nations to adopt Christianity as their state religion, the other two being Armenia and Georgia. However, it appears that the Sabaens as mentioned in the Quran were Manacheans, followers of the self proclaimed prophet Mani, whose brand of monotheism was a Christian, Jewish, zoroastrian mix, with Mani even claiming decendency of Buddha.
A few more choice tidbits:
Persepolis, a Greek name, is named Takhtejamshid by Iranians, the throne of Jamshid. Jamshid being a mythical king, the first man, even, who ruled for a 1000 years. The Sassanids, with their Zoroastrian clergy, reworked history to cast themselves as the primordial rules of Persia, had themselves forgotten history only some 800 years old, forgetting Cyrus, the actual king who ruled from Persepolis, whose throne room was not destroyed by a demon, but instead by the demonic Alexander, remembered in the Quran as the two-horned one.
The Arab term for believer is mu'min. Is there an offhanded needling in the name of the Finnish animated series Moomin?
The nomads of Mongolia adopted a version of the Syriac script as a result of the fanning out of Nestorian Christians under early Arab rule. The growth of the Nestorian church being the result of the collapse of the Zoroastrianism, former zoroastrians becoming Nestorian.
But also Islam was a welcome alternative for zoroastrians. So much, in fact, that parts of popular Islam were shaped by this influx of that old religion. The Quran only prescribes praying three times a day, where it was the Zoroastrian church which prescribed five. Unbelievers, according to the Quran, would go to hell, but it was Zoroastrianism which prescribed execution.