I read The Mists of Avalon much later in my Arthurian reading career. I think I must have started off with the straight retelling of the legends by Roger Lancelyn Green (friend of C.S. Lewis) and I think I went on then to Rosemary Sutcliff (I don't know how much her work has travelled outside the UK). She wrote a straight historical novel based on Arthur called Sword at Sunset which I absolutely loved. Then I moved on to Mary Stewart. Oh and T.H. White was in there somewhere as well. You're making me nostalgic... And you're absolutely right that there's been no good visual version. It just doesn't seem to translate well. The BBC made a horrendous mess of The Crystal Cave by realising that they couldn't show the machinations surrounding the birth of Arthur at Sunday teatime!