Bjork's unearthly voice swoops and careens, so she makes pop music to match, where you never know whether to expect a techno rhythm or a string section. Like the songs of Iceland's other leading exports, Sigur Ros, her music feels foreign — which not much on this planet does anymore. But thanks to her frequent collaborator Nellee Hooper, her naive, eccentric roundelays are often grounded in solid dance-floor grooves (in England, she even has hit songs). This retrospective compiles fifteen tracks, none from Selmasongs, the soundtrack to the harrowing 2000 film Dancer in the Dark. The best is still "Human Behaviour," her kettledrum-heavy single from 1993. The only disappointment is that Bjork titled a best-of collection something as banal as Greatest Hits. At this rate, she won't even wear a swan to the Oscars anymore.