One of the most compelling early Franciscan writings is called Sacrum Commercium*, a spiritual allegory, which was most likely written shortly after Francis's death. While the authorship is open to speculation, I personally favor the argument for Thomas of Celano. At any rate, what is most intriguing about this beautiful writing, is what it shows of the early Franciscan understanding of poverty in the spiritual life.
'Blessed are the poor/Blessed are the poor in spirit'...is interpreted broadly in the Church: individuals react and are affected by its demands in various ways. Yet for Franciscans the meaning is circumscribed by the radical witness of Francis himself. Indeed, the evangelical council of poverty is to be taken as foundational in understanding the Franciscan way. It is lived differently depending on one's state in life, nevertheless it has a primary meaning for the spiritual family as a whole. Of course, Francis is to be taken seriously, as he is ascribed the title 'Mirror of Perfection' and 'Altere Christos', for many good reasons beyond the scope of this reflection.
The designation of poverty as 'Lady Poverty' is attributed to Francis himself. She was his personal spiritual love; in whom he invested the quality of persona...the ability to speak and act and teach us in all wisdom...about the love that the Father has for us, which culminates in his sending his only begotten Son to redeem us.
In one scene, Lady Poverty is present in the Garden of Eden before 'the fall'. She relates;
"I was rejoicing exceedingly and playing before him [Adam] all the while, for possessing nothing, he belonged entirely to God."
In this one sentence she reveals a marvelous insight into the blessing of poverty. This writing rises almost to the level of inspired scripture in that it can be read again and again with ever deepening insights. I highly recommend it.
* This abbreviated title is difficult to translate and is loosely held as "The Sacred Romance of St. Francis with Holy Lady Poverty".