An idea someone else will make money off of

Self-help books written by the mentally ill. If done correctly, they could make for funny reading, as well as provide insight into abnormal thought processes, in much the same way you can learn about autism by reading A Class in Spookville or Sonichu*

You could start with Seven Habits of the Highly Effective Sociopath, then move on to Who Moved My Cheese, and Who is He Working For? (from the paranoid), I'm OK, I'm Not OK, I'm the King of Alaska (bipolar I), He's Just Not That Into You, Probably Because of Something You Did, Now He's Leaving You Just Like Daddy Did, He Can't Do This! (borderline personality), Everything You Would Want to Know About Sex, If You Cared (schizoid), and What Color is Your Parachute? Mine is Red. You Know, Leonardo da Vinci Designed a Parachute in the 1600s, But The First Successful Parachute Was Tested in 1783 by Louis-Sebastien Lenormand… (Asperger's)

*note that this particular rabbit hole goes down quite deep, and contains some non-work-safe material