I found Rumi an exceptionally imressive thinker. His prose is compelling. Poetry though sounds simple, is thought provoking.
Rumi’s poetry is wide ranging and encompasses many different ideas but behind all the poetry the essential theme was the longing and searching for the union with the divine. Rumi was himself a great mystic. His outpourings of poetry were a reflection of his own inner consciousness. Ironically Rumi said that no words could adequately explain the experience of mystical union. Yet his words are inspiring signposts which point towards the divine.
In his poetry Rumi frequently uses imagery which may be unexpected. For example although Islam forbids alcohol, he often describes the sensation of being “drunk and intoxicated with ecstasy for his beloved." Here drunk implies the bliss of the divine consciousness. Love is a frequent subject of Rumi's poems, descriptions of seeming romantic love is an illusion to the all encompassing pure, divine love. Metaphors such as this are common to other Sufi poets such as Omar Khayyam, Hafiz, and Attar.
Rumi's poetry is so widely appreciated because it has the capacity to uplift our own consciouness. Reading the words of Rumi can awaken in ourselves, our own spiritual self.
Here is a poem of Rumi.
Is that not what all great people told?
It need not be esoteric.
Simple facts are enough.
I found only the English version.
Translations are mine.