Our housemate had to watch this for a writing class in college, and while it doesn't adhere strictly to the original story, it was far better than I had expected. The movie is well shot and well scripted, and I thought the actors did a good job and showed plausible reactions and natural behavior within the confines of the story and plot. This was only the second or third movie we have stream live off the internet, and despite streaming on a two year old computer, the video quality and presentation were excellent--no stopping/starting, no lagging, no buffering. As those are all problems we routinely experience while watching videos on other streaming services (despite having cable internet, 100 mps speeds), we were happily surprised at how well the Amazon streaming works.
If you're a Tristan and Isolde fan, I would recommend watching this film, despite some of the variance from the original story. If you've never heard of Tristan and Isolde, this would be a good place to start as well. For the literature purist, the few deviations it has are forgivable ones :-)