I have vague memories of pop culture references to King Arthur and Sir Lancelot while I was growing up, but I first learned the basics about the legends in high school, when my English class read Tennyson's Idylls of the King. The teacher also told us about Thomas Malory's Mort d'Arthur, on which it was largely based, and some of the ways in which Tennyson departed from his source material.
I was hooked. In college, I took as many literature electives as a business major could manage to fit in and began reading some of the earlier medieval versions. For recreational reading, I devoured many of the modern retellings (some with a high medieval or fantasy setting, some firmly set in a realistic late-Roman-Britain setting). My favorites were those by authors who Arthur Rex: A Legendary Novel and Sharan Newman's Guinevere trilogy. No matter how many times I read the story, however, I always knew going in that there would be no happily-ever-after.
I got away from the Matter of Britain for a number of years, largely because the pressures of post-college life led me to want a happy ending in my recreational reading. My interest in Arthurian stories was re-kindled by a trip I took to Glastonbury last summer. I climbed the tor and saw the purported grave of King Arthur (conveniently found by the monks in the 12th century, when they desperately needed pilgrims and donations to help them rebuild the church after a fire). I remembered my love for the legends and their many retellings.