Proof Islam is really a copy of Zoroastrianism / "The Quran is really a Persian folktale" [contains major elements taken from pre-existing Persian folktale]
Islam is a copy of Christianity, Judaism, Zoroastrianism and Arabian paganism. It doesn't have much new things to "reveal", most Islamic elements have already existed before.
The Phoenix Order is a book in the series. It contains stories that show the morals and life of a young boy with magical powers, a boy with a parenthood shrouded in mystery and a potent, evil adversary.
The religions of the time were a continuation of older ideas and sought inspiration in what people knew.