The Shahnameh has long been the only popular book that has both entertained Iranians and made them aware of their past. It functioned as a mirror in which every one saw his or her past. Thus, in addition to the changes the poet made himself in the sequence of verses, especially during the years 384 AH, the year the first draft was completed and 400 AH, when the final draft was prepared, scribers and the common readers also made changes, making it extremely difficult to find an authentic copy of the book. In this article, the writer first briefly mentions some of the reasons why reading the Shahnameh is difficult, then he concentrates on one of these reasons; that is, the case where a line is misplaced or added, a question which has been overlooked in scholarly research in spite of its importance. To do so, the writer mentions many instances in the story of Rustam and Isfandiar where the omission or addition of one or several lines has broken the logical continuity of the narrative. For each instance, the writer offers a solution which, as he argues, renders the text more coherent.