Book 11: Switching Time: A Doctor's Harrowing Story of Treating a Woman with 17 Personalities, by Dr. Richard Baer
Another book where the title/sub-title pretty much sum up the plot, this was the memoir of a psychiatrist who, over the course of 16 years, treats a woman with a true case of multiple personality disorder.
Spawned as a coping mechanism to deal with a cycle of abuse that started well before she was born, "Karen's" MPD helped her get through years of abuse - from her father punching her mother's stomach while she was pregnant to ritualistic quasi-religious physical and sexual abuse. The journey is definitely interesting to follow as we watch Karen learn of her "alters" and eventually cope with having them.
Perhaps something fiction next...