I'd think that was a silly idea, but a similar book exists from a similar time period attempting to "defend" Judaism. Ha-Kuzari: A Defense of the Despised Faith -- the author's title, not mine -- purports to be a record of the conversation that took place between the King of the Khazars and a rabbi that led to the Khazar conversion to Judasim. The conversion of the Khazar nobility, at least, is an established fact, but the document is of course not an actual record of the conversation, but merely uses that conceit as an expository excuse :-).