The casual Bjork listener doesn't exist, because with her it's either sink or swim. It's either you like her or not. Those who like her love her to death, and those who don't probably hate her for being "weird." Many people couldn't get past Bjork's image and are scared to listen to her (I was) because they think she's too avant garde or too out there for their tastes. But what's so surprising about her music is the more her music sounds experimental, the more naked and personal her lyrics become.
Bjork also has one of the greatest voices in music, and she uses it to blend or clash with her electronic blips and squeals and the occasional string quartet, to suit whatever she's trying to achieve. Her transportive and adventurous albums Post and Homogenic are modern classics, and her songs like Hyperballad, The Modern Things, Joga, Hunter and Pagan Poetry, are masterpieces. Required listening for the human race.