One of the greatest roles that Robin Williams hoped — but never got the chance — to play is coming back around, with a new edition of First Person Plural: My Life as a Multiple , Cameron West’s memoir co-written with wife Rikki West, hitting shelves May 26. The original 1999 book offered an intimate window into West’s experience living with dissociative identity disorder, formerly known as multiple personality disorder, as his dozens of alters developed out of severe childhood trauma.

West, now a Ph.D. in psychology, struck a chord throughout the world by unflinchingly telling his story.…