The "Divan" is the inspiration of Rumi's middle-aged years. It began with his meeting Shams-i Tabriz, becoming his disciple and spiritual friend, the stress of Shams' first disappearance, and the crisis of Shams' final disappearance. It is believed that he continued to compose poems for the Divan long after this final crisis-- during the composition of the Masnavi.
The Divan is filled with ecstatic verses in which Rumi expresses his mystical love for Shams as a symbol of his love for God. It is characteristic of Persian sufi poetry for it to be ambiguous as to whether the human beloved or the Divine Beloved (= God) is being addressed. It is also an essential feature of the particular kind of sufism Rumi practiced that mystical "annihilation in the spiritual master" [fanā fi 'sh-shaykh] is considered a necessary first stage before mystical "annihilation in God" [fanā fi 'llāh] can be attained. The Divan is filled with poems expressing this first stage in which Rumi sees Shams everywhere and in everything. Rumi's "annihilation" of his separate self was so intense that, instead of following the tradition of including his own name in the last line of odes/ghazals, he often uses the name of his beloved spiritual master and friend instead. Or he appeals to (mystical) Silence [khāmosh] which transcends the mind and its concepts.
"Divan" [Arabic: dīwān; pronounced "dīvān" in Persian] means the "collected works" of a poet. It has been published with a variety of titles: "Dīvan-i Kabīr," "Dīvān-i Shams-i Tabrīzī ," "Kulliyāt-i Shams," "Kulliyāt-i Shams-i Tabrīzī."
Rumi's Divan consists of three different types of poems. It contains 44,282 lines (according to Foruzanfar's edition, which is based on the oldest manuscripts available): 3,229 odes, or ghazals [ghazaliyāt] (total lines = 34,662); 44 tarji-bands [tarjī`āt] (total lines = 1698); and 1,983 quatrains [rubā`iyāt] (total lines = 7932).
The best edition available was done by the Iranian scholar, Badi`uzzamān Forōzānfar, published in ten volumes between 1957-1967.
There is a also a (widely distributed) commercial edition in one volume ("Kulliyāt-i Dīvān-i Shamsī Tabrīzī," published by Amīr Kabīr, 1957, enlarged 1962, and re-printed many times since), which falsely purports to contain all of Foruzanfar's edition. However, it was first put out before Foruzanfar completed the last section of ghazals (finished in 1966), all of the tarji-bands, (finished in 1966) and all of the quatrains (finished in 1963). Therefore, the one-volume edition contains Foruzanfar's authentic work (minus his variants and footnotes) only up to ghazal number 3106. After that, the rest of the volume consists of poems incorporated from other (inferior sources) and not from the earliest manuscripts. This includes the ghazals (numbered 3107-3365), all the tarji-bands (numbered 3366-3502), and all the ruba'iyats/quatrains (numbered 1-1995).