In pop-music circles, Suzanne Vega is known almost entirely for two songs from the late 1980s: the child-abuse ballad "Luka" and a song that launched literally dozens of dance remixes, "Tom's Diner." But Vega has been making vital, inventive music the entire time — much of it folk-based, though her sound has taken many smart detours along the way — and is about to put out her first album of original material in seven years, Tales From the Realm of the Queen of Pentacles.