Verdi's Simon Boccanegra exists in two versions: that of the 1857 original and that of the 1881 revision. The texts of the libretto of both versions are included in this guide, with a number of essays which focus on the differences between the two. Rodolfo Celleti provides the story's historical context, setting the events of the real life of Simon Boccanegra against the unification of Italy, which formed the political backdrop to the composition of both versions of Verdi's opera. James A. Hepokoski gives a detailed synopsis of the 1881 score, and indicates the ways in which Verdi radically revised the original and reworked it to fit his late style. Lastly, Desmond Shawe-Taylor discusses Verdi's attitude to his singers, and the critical reception that performances of both versions of the opera received.