The poem is separated into twelve "books" or sections, the lengths of qui Vary Greatly (the longest is Book IX, with 1,189 lines, and the shortest Book VII, with 640). The arguments at the head of Each book in Subsequent Were added imprints of the first edition. Originally published in ten books, has fully "Revised and Augmented" edition reorganized into twelve books Was Issued in 1674, and this is the edition Generally used today.
