Not bad; different.
To unreceptive ears the drummer may seem not to be reading from the same sheet music as the other players, her beat klunking along like cardiac arhythmia. To other ears the vaguely Eastern-flavored music sounds entirely improvisational and the players completely unacquainted with each other as musicians, perhaps even as human beings.
Not the case.
It's not that the guitar, voice, and drums are "playing a different song." It is that sometimes the guitar is syncopated while the drums are not, sometimes the reverse. They're playing both ends of the beat at once -- kind of like Robert Fripp & Co. did with Discipline. The music can be described as Eastern only in that the players are from the East coast of the U.S., and is not improvised at all; the singers sing more or less in unison, with something approaching harmony -- evidence of forethought, however skewed. Furthermore, the players are fairly well acquainted with one another, being three sisters of the Wiggin family of New Hampshire.
Depending largely upon your general outlook on life, you'll either see the Wiggin sisters as talent show no-talents or harbingers of an entire new musical vocabulary. If we're lucky.
Update, dec1999: Here's some Shaggs news from Hollywood. Depending largely upon your general outlook on life, you'll either see it as good news or bad news, but news it is ... the Shaggs's own story (heh) has been optioned by ... Tom Cruise. Yep.
I say, buy the CD immediately, before The Shaggs suffer the Taint of Tom. Or the Taint of Tom's Taint, depending upon what rating the filmmakers are going to go for.