It is primarily about why Orthodox Jews do not accept secular scholarship about the origins of the Torah — that it is a post-Mosaic composite work. Orthodoxy posits that the Torah came directly from God to Moses and every word of it is divine and binding upon us Jews (as interpreted by the rabbis).
Despite his heretical beliefs, Schimmel belongs to an Orthodox synagogue.
On page 13, he writes that his Orthodox beliefs, values, emotions, behavior and community "have weakened as a consequence of my skepticism, and their replacements have not been as intense, vigorous, joyous, and existentially meaningful as was Orthodoxy."
Schimmel wants to convert the Orthodox to his way of thinking, thus robbing them of the same joy and meaning he once had.