"Beauty is truth, truth beauty," wrote the Romantic poet John Keats in his "Ode on a Grecian Urn," and those lines could just as well describe the short arc of his own life. The rest of the line, "that is all ye know on earth, and all ye need to know," defines precisely the "in-the-moment" philosophy of this poet who, with a mere fifty-four poems to his credit, has captured the imaginations and sentiments of generations since his death in 1821. Keats was one of the short-lived stars in the firmament that the Romantic age seemed to launch--Lord Byron and Percy Bysshe Shelley were others--who died young and left a lasting legacy in the world of letters. Byron was thirty-six at his death, Shelley thirty-two. Keats, dead at twenty-five, differs from the other two in that he was not born into the aristocracy or the upper classes; rather, he...