Loser's Guide to Life
I never read any of Horatio Alger's books, though I have been periodically sickened by literature of the period exuding the same practical piety, and I assumed he had been a successful businessman who liked to bore people with worthy examples. I assumed his stories had some basis in fact, maybe fictionalized accounts of the early years of other self-made industrialists. I was unaware that it was all complete nonsense, that he was a failed preacher, knew nothing of business, and was in fact an out-and-out pedophile addicted to chasing boys. See the Wikipedia entry (via a comment at Eschaton).
In the Wikipedia entry the common plot of Alger's novels is boiled down to the idea of a poor boy who is taken in by some wealthy man, as hard work alone doesn't account for much. This means that the enormously popular works were nothing more than a pimp's advertisements.