I read this hoping to get a clearer picture of Katherine Swynford (of 'Katherine' by Anysa Seton fame).
I ended up with a much clearer sense of John of Gaunt, Henry IV and Edward III. Which is fine, but not what was intended.
So, do I recommend it? If you have an interest in this particular period of history, this may either augment knowledge you already have or give a starting point. If you're looking for the definitive story of Katherine Swynford - I doubt that such a book can now be written. It's a pity: the snippets of history we have indicate that she was a fascinating woman.