The Oxford Dictionary of National Biography emphasizes details of people's lives. It can be useful to situate your knowledge of your subject.
The Dictionary of Literary Biography and Biography in Context database, however, provide both overviews of your person's life, and discussions of their major works, influences, critical receptions, and legacies.
Although the Oxford Dictionary of National Biography and Dictionary of Literary Biography are print Reference books, they are well worth the trip to the Berry Library Reference area. These multivolume sets have much useful information.