Susan Sontag has said that her earliest idea of what a writer should be was "someone who is interested in everything." Thirty-five years after her first collection of essays, the now classic "Against Interpretation," our most important essayist has chosen more than forty longer and shorter pieces from the last two decades that illustrate a deeply felt, kaleidoscopic array of interests, passions, observations, and ideas. "Reading" offers ardent, freewheeling...