I fell in love with the Arthur story at first through the novels of TH White, then through Marion Zimmer Bradley's The Mists of Avalon (though that particular novel has been ruined for me after learning about Bradley's disturbing personal history). But Mary Stewart's trilogy, published in the 1970s, has become a classic re-telling. Stewart's Merlin does have magical powers, especially the power of prophecy, but his magic is exaggerated by the population, who fear and revere him. I must admit that the battle scenes and sword fights, of which there are quite a few, were not so interesting to me as the personal relationships and the growth of Merlin's legend. (In this telling, Merlin does raise the stones of Stonehenge, but with sound engineering rather than pure magic.)
The Crystal Cave ends just where the Arthur legend really begins, with King Uther sneaking into Tintagel to meet Igraine, disguised as her husband (with Merlin's help), and the conception of the child who will become King Arthur. I've now embarked on the next volume, The Hollow Hills, which picks up exactly where The Crystal Cave finishes, and I'm looking forward to finishing the rest of the trilogy.