Complex sentence: A Preface establishes his main theme of the uniqueness of Shakespeare's characters and looks back at earlier Shakespearean criticism, and two concluding chapters on "Doubtful Plays of Shakespear" and the "Poems and Sonnets" round out the book.
Split into simpler sentences: A Preface establishes his main theme of the uniqueness of Shakespeare's characters and looks back at earlier Shakespearean criticism. Two concluding chapters on "Doubtful Plays of Shakespear" and the "Poems and Sonnets" round out the book.