I chose that particular reference because the authors are Christians. A Christian who really wants to know how Christianity originated is an exceedingly rare person. Freake and Gandy were students of Arnold Toynbee. They spent years in search of the historical Jesus. They never found him. What they found instead is in their book.
"Christianity obviously got started somewhere. You assert(with no proof whatsoever) that it was invented in Egypt. I could take that on faith, but I won't." -- A.J.
Don't take it on faith. Undertake the search yourself. While you are at it you might see what you can find out about the origins of Judaism. The original god of the Jews was the tribal genie of the Bedouin Khabiru who occupied and activated a volcano in northwest Arabia. The Hebrews learned of monotheism during the Babylonian Captivity -- another case of cross-cultural insemination leading to the birth of a novel religious form.
"The early Christians were often killed for their beliefs." -- A.J.
Some were. Far more Pagans and Gnostics were killed by the Literalist Roman Church though. The persecutions were in reality very mild and generally done as a last resort effort to quell the rising disruption brought on by the unruly mobs of Christians many of whom demanded martyrdom in order to go quickly to their eternal reward. Often, the Roman official who refused to grant such a request was himself put to death by the Christian mob. These little anecdotes from the early days of the Church do not often make their way into the children's catechism. Remember that the victor writes history to suit himself. The literalist Roman Church was victorious and most of the more sordid references to its early days have been removed from the popular histories or they would never have been published. You have to dig a little deeper if you want the whole story.
"If something like the story in the Gospel didn't happen, there'd be no Christians and thus no Scriptures." -- A.J.
It is the other way around. The stories came first. The Mystery Cults of Dionysus, the temple at Eleusis, the symbolic resurrections of 30,000 followers at a single event, were well known to most people of that time. Christianity is just one such cult with many variants. The variant that became the literalist Roman Church destroyed the others because of its ruthless nature and the reliance on dogma and literal historicity. For followers of the other resurrecting god/man cults the lessons of the religion were entirely spiritual and allegorical. No historical factuality was assumed or necessary once the follower had been initiated into the "Mystery."
"You're projecting your image of modern fundamentalists, with coloration provided by Islamists, on to ancient Christians. It doesn't fit." -- A.J.
I beg to differ. By their acts you shall know them. Wholesale destruction of anything and everything written was responsible for the demise of Pagan Civilization. Even owning written material could result in death at the hands of the Christian Mobs. The Taliban are well mannered and thoughtful preservers of alternative creeds by comparison with the early Christians who even destroyed what was best and truest in their own tradition in favor of a few paltry texts that were largely copies of each other or later forgeries that supported the political motivations of the orthodox hierarchy of Rome.