This 1976 effort is among ABBA's best full-lengths. To begin with, it boasts "Dancing Queen," the group's only U.S. No. 1 hit and what may well be their most covered song. Almost as good, "Knowing Me, Knowing You" pulls the usual ABBA trick of turning loneliness and alienation into catchy pop. Songs not only withstand repeated listens, they continually reveal new sonic layers. Even lesser-known tunes, such as "Dum Dum Diddle," are loaded with hooks. Bonus tracks include "Fernando" and the B-side of its single, an early version of "Why Did It Have to Be Me" called "Happy Hawaii." --Elisabeth Vincentelli