"The Private Memoirs and Confessions of a Justified Sinner"
This book is 19th-century Scottish writer James Hogg's sole remaining claim to fame. It's a good one, too, kind of a mixture of a religious satire and a gothic. The story is about a young man who is raised to believe that since he is one of the "elect" there won't be any ill effects if he sins. Unfortunately this leaves him vulnerable to demons, one of which persuades him that he should become a holy assassin, murdering such deviants as ministers who teach the blasphemy that good works are the route to salvation. And his brother. And his father. Or maybe the demon doesn't exist at all. It's a bit ambiguous that way--the book has an interesting format, with a long introduction (80 pages) purporting to be historical, which lays out most of the story, followed by slightly longer section of "memoir", and of course there are discrepancies between the two versions.