The Masnavi

Stories are told to illustrate a point and each moral is discussed in detail. It incorporates a variety of Islamic wisdom but primarily focuses on emphasizing inward personal Sufi interpretation. In contrast to Rumi's Diwan, the Masnavi is a relatively "sober" text. It explains the various dimensions of spiritual life and practice to Sufi disciples and anyone who wishes to ponder the meaning of life. It was left unfinished at the time of the demise of Mawlana Rumi but he said in the last few line of the book that another pious person will come to complete the book and the Sunni Muslims believe that man to be Mufti Ilaahi Bakhsh Kandhlawi, who authored Ikhtimaam-e-Mathnawi as an addendum and the completion of this magnum opus. 

Books 1 and 2: They "are principally concerned with the nafs, the lower carnal self, and its self-deception and evil tendencies."
Books 3 and 4: These books share the principal themes of Reason and Knowledge. These two themes are personified by Rumi in the Biblical and Quranic figure of the Prophet Moses.
Books 5 and 6: These last two books are joined by the universal ideal that man must deny his physical earthly existence to understand God's existence.