Nevo's work falls squarely into the "Hagarist" tradition that radically reinterprets early Islamic history. For the most part, scholars of early Islam—even Patricia Crone and Michael Cook, authors of Hagarism—have avoided the full implications of this interpretation because of the almost complete lack of non-Muslim sources and the difficulties in working with the tendentious Muslim ones. Nevo and Koren overcome this problem by focusing upon sources not usually adduced by scholars of Islam: archeology and epigraphy. By examining the archeological remains (and in some cases the lack thereof) of the early Islamic period, the authors call into question the standard accounts of Muslim conquest that are still cited as fact in most history books. They supply a vast selection of inscriptions hitherto unnoticed and uncited in the standard histories, which for the most part are datable to the seventh and eighth centuries, and use them to build a historical theory considerably different from the standard account.
Nevo's theory is that Arab history—specifically not Islamic history—is completely a construct and cannot stand up to historical examination on the basis of non-Muslim sources. His theory surmises that paganism was far more deeply rooted in pre-Arabian society than was previously thought and that much of what we now call early Islamic history records the development away from that heritage into a monotheistic belief-system that did not reach perfection until the ninth century at the earliest.
For the most part, Crossroads employs a very rigorous, historical methodology, focusing exclusively upon those sources datable from before the ninth century, which usually means non-Muslim ones. These sources provide a view of Islam that lacks the preeminence of Muhammad and the exclusivity of later Islam. This reviewer finds much of Nevo and Koren's work to be plausible or at least arguable, and it certainly presents a powerful challenge to the mainstream view of the origins of Islam.
It is a pity that Nevo and Koren do not include the work of Fred Donner, who also has come (from a more mainstream approach) to reject the early exclusivity of Islam. More broadly Crossroads to Islam suffers to some extent from a lack of cited scholarship after the early 1990s, which is a pity.
One area, however, where this reviewer disagrees with Nevo and Koren concerns their theory, following John Wansbrough, of the Qur'an as the product of a redaction during the ‘Abbasid period (eighth-ninth centuries). While agreeing that the historical narratives of the conquests are highly problematic and for the most part probably fanciful, they do represent, according to the historical memory of the Arabs, the supreme confirmation miracle of Islam. If the Qur'an were redacted at such a late date, when numerous datable hagiographical accounts of the conquests already existed, these accounts would surely have been represented within the text of the Qur'an. Their absence pushes the date of the Qur'an back to the earlier period.
Other than that, the account given by Nevo and Koren must be seriously considered by scholars of early Islam.
 Hagarism: The Making of the Islamic World (Cambridge: Cambridge University Press, 1977).