The general outlines of Vincent van Gogh's life--the early difficulties in Holland and Paris, the revelatory impact of the move to Provence, the attacks of madness and despair that led to his suicide--are almost as familiar as his paintings. Yet neither the paintings nor Van Gogh's story might have survived at all had it not been for his sister-in-law, the teacher, translator, and socialist Jo van Gogh-Bonger. Jo married the painter's brother,...