3.5 stars, rounding up to 4. My favourite of Walton's Mabinogion retellings thus far, I think because the conflict here is primarily internal rather than a series of battles in which relatively unsympathetic characters take part. There's still plenty of action, but the action here is more metaphorical - when Pwyll is fighting the bird-demon, for instance, it's clear that the bird is representative of self-doubt rather than a straight-up feathery monster. And because the story is so focused on Pwyll's internal journey, I ended up feeling more for him than I do for most of Walton's other characters - while realising that this series is well-written, I've felt little emotional response to the previous books. I actually cared about what was happening here (on top of admiring the technique of it all) so that was an improvement.