If you would like to read another novel about Constance of York after digesting Within the Fetterlock, you could try The White Rose of Langley by Emily S Holt which is available through
I do have to warn you though that Ms Holt is a Victorian writer and her views about the Roman Catholic Church in particular are distinctly non-PC. (If you are wondering, all the 'good' characters are, or become, Lollards.) I should hate anyone to be offended.
It is, nonetheless, an interesting read in parts and you may enjoy comparing and contrasting her interpretation of Constance against mine.
Oddly enough, I can't think of any other novel that focuses on the House of York in its early years, though there are a number written around the Lancaster bunch.