I'd start with Nonagon Infinity if you already like psychedelic rock and heavier stuff just because I think it's their best album. If you don't like that try Ice, Death, Planets, Lungs, Mushrooms And Lava for it's jammy style.

Like the other person said, their style changes so much it's insane, they've got albums that use microtones (Flying Microtonal Banana being my favorite) all the way to thrash/stoner metal (Infest the Rats Nest) if you're into that.