I don't know why, but I was very surprised about how good this turned out to be. The story is a poem set in the Arthurian world and written by an anonymous author in the 14th century. The story is very tight and well developed. The poetry is alliterative, which I thought might have sounded like a picture book, but works very well.
There are some very clever scenes and bits of description. My favorite part is the third Fit (part) where scenes of attempted seduction of Gawain are intermingled with hunting scenes. Gawain is an interesting very virtuous hero, which is very hard to do. He has the typical virtues of a chivalric knight but manages to remain a person with foibles despite that. Most noticeably he excoriates himself for what everyone else including the author see as an almost totally insignificant failing and which the modern reader is unlikely to see as anything other than good commonsense.
The most interesting figure of all is the Green Knight. Its easy to see him as a demonic figure. He appears to be theoretically an enchanted knight. I think that he is clearly rooted in pagan figures and faerie lore. There is a lot of the Green Man in the Green Knight. Even though the morality of the poem is fundamentally chivalric, which is a form of Christian morality, one can't see any real Christian concepts at all in the Green Knight who is richly drawn and a fantastic character as also is the wife of the Lord who Sir Gawain stays with.
All in all it is very effective. I had suspected that Sir Gawain and the Green Knight had been seized on by SCA types who wanted it to be good, but it is in fact really really good.
A lovely surprise.