Ooh, nice find at Google Book: Christine de Pisan's The Book of the Duke of True Lovers.
The book of the Duke of true lovers By Christine, Christine de Pisan, Alice Kemp-Welch, Laurence Binyon, Eric Robert Dalrymple Maclagan
I hadn't come across it before; judging from the translation, it looks like the original was prosimetric, which would be fairly unusual -- prosimetric works are hard to write because you have to integrate very different ways of writing. It's rather difficult to find Christine's works in English, despite the fact that she was one of the great early modern writers. And while I am still reading it, it's Christine de Pisan, so you know it's going to be good.