''Maggie: A Girl of the Streets,'' Stephen Crane's first novel, is the story of a beautiful young girl living in the slums of New York in the late 19th Century. ''Maggie: A Girl of the Streets'' is a shockingly explicit portrait of the brutal conditions that existed in the poverty-stricken slums of New York. Originally refused by all publishers that it was submitted to because of its brutal and sexual realism, ''Maggie: A Girl of the Streets'' was first published by Stephen Crane at his own expense.