Not the only ballad

There is a whole sub-genre of Tam Lin fanfic, so to speak: Diana Wynne Jones's Fire and Hemlock (the first I read and still my favourite, Elizabeth Bear's splendid Blood and Iron, Pamela Dean's Tam Lin (which I have only just read and enjoyed)...

But the sound of durham_rambler's newest CD (Liege and Lief) thundering through the house prompts the question, why has no-one written a novel based on Mattie Groves? I'd pay good money for a book that made sense of the behaviour of the lady in that tale!