I was delighted to read, on Sharon K Penman's Blog that she is planning to write a novel about Owain Glyn Dwr. (She also says kind things about Alianore Audley, but that's another matter.)
A novel on Owain is long overdue. The last really good one was Owen Glendower by John Cowper Powys, which was published before the Second World War. While it's a 'great' book, I wouldn't describe it is accessible - in fact by comparison your average Dorothy Dunnett is a young adult short story. So I'm really looking forward to the Penman version, and to what she will make of Owain, Bolingbroke, Grey de Ruthin, Edmund Mortimer and all our old friends.
For the present though, if you've got two weeks on a beach and a burning interest in Owain, you could try the Cowper Powys account.