I've spent a little while here tonight for the first time and noticed that a lot of people have some confusion about whether this current Merlin series adheres to the legend.
In the spirit of giving both fans and detractors of the show who seem to not be familiar with the fact that there are many interpretations of the legend/myth, here are some must-read books which, if you are a serious Camelot-era fan as I am, you really must read. Books which you will live in as you read them.
Mary Stewart's version is can't-put-down stuff. I read some of her other work 50 years ago and so was already familiar with how she pulls in readers. The first time I picked one up, it was the last volume in her initial trilogy, and as I found the other two, I read them also. It turned out that I'd read them in the wrong order because I didn't at first know it was a trilogy. So as soon as I'd finished the last book, I read all 3 from start to finish again in the correct order. This woman knows how to write! The subject had always drawn me to it, but after this, I was completely hooked.
After that, I could not help but to find and read T.H. White's Once and Future King
And the last series I read was by Jack Whyte, a 6-volume set. It was a completely different take on the story, since it isn't until the end of the 6th book that Arthur pulls the sword from the stone. The whole thing is about the politically-realistic generational history which led to that point, and at that point in my life, I felt fortunate to be able to take two months off over a summer, because I just could not put it down. As Wikipedia puts it, "The tacit implication is that Whyte's version of history is the true story that has become distorted over time to become the legend and stories of magic that we know today."
Anyone who reads all of these books will immediately understand the characters in this "Merlin" series and have a good, solid foundation for understanding what this series is trying to do, and if one is flexible-of-mind, should be able to enjoy it as much as I do. Which, it should go without saying, is a LOT. I haven't missed a single episode. Nobody / nothing comes between me and my watching Merlin on Saturdays at 5 pm!