Growing up in the fifties, Carolyn Spiro was always in the shadow of her more intellectually dominant and social outgoing twin, Pamela. But as the twins approached adolescence, Pamela began to succumb to schizophrenia, hearing disembodied voices and eventually suffering many breakdowns and hospitalizations.

Divided Minds is a dual memoir of identical twins, one of whom faces a life sentence of schizophrenia, and the other who becomes a psychiatrist, after entering the spotlight that had for so long been focused on her sister. Told in the alternating voices of the sisters,...