The author takes the way most traveled in fictionalizing the sparsely documented life of Michelangelo Merisi, ""Caravaggio,"" (1573-1610), the Italian painter whose realistic, dramatic, religious canvasses were to have an enormous impact on technique and concept far into the next century. Caravaggio's masterpieces--which here seem to pop up perfect and glistening like bottled cola--are secondary to matters of bread, bed, and brawls. And Caravaggio's oft-mentioned fracases are presented as the result of a good and upright heart fighting off injustice and cruelty. He rescues his friend, apprentice, and aide de camp, Gian, from a dank cellar where, as a mere boy, Gian had been incarcerated by a wicked stepmother. Maddalena, the artist's beautiful model, mistress, and mother of his child, is lifted up by him from lonely, starved, pregnant wretchedness. Another young girl is snatched from abuse and a brothel. Yes, in spite of help and intervention from kindly noble patrons, a man will make enemies if he fights for honor and innocence. And, following Caravaggio from a grim, brutalized boyhood to Milan, Rome, Naples, and Malta, Murray puts down the rumor that he was a homosexual--through a series of active lay-downs with Maddalena. A routine commercial paste-up, in construction paper colors, bearing little relationship to the subtly emotive chiaroscuro of the painter's art.