In Book Twelve of the Florentine Codex, the encyclopedic work on ancient Mexico of Franciscan friar, Bernardino de Sahagún (1499–1590), he focuses on the history of the Spanish conquest. It includes the Nahuati text and Sahagún’s translation into Spanish. The original 1579 manuscript was subsequently revised by Sahagun in 1585 and although the original has been lost, in 1970, John Glass found another copy of the Spanish translation in the Boston Public Library. This was made available to Howard Cline for a project to create an edition of all available versions of Book Twelve. The project was continued and completed by Susan Cline, resulting in the present book. It includes facsimile editions of the Boston manuscript, and notes and opinions by the Mexican scholar Carlos María de Bustamante taken from an 1840 publication. It also includes a transcription of the Boston manuscript and an English translation of the same made by Howard Cline. A fuller history of this work is provided in the introduction by Susan Cline, explaining the differences and possible explanation for the changes between the 1585 revision and the original manuscript.