Kool Keith is different. Can be considered nerd rap or underground but Kool Keith has probably hit every chamber of hip-hop besides real gangsta rap...but to answer you I would start with
Ultramag from start to finish
Put Sex Style/Matthew/Black Elvis to the side
Listen to First Come, First Serve then The Return of Dr. Octagon
If you like that then go through the rest of his shyt

I enjoyed it but most likely won't replay it. Probably will jump to Four Horsemen later on.

Ok I'm on Housing Authority. Brotha what do you have me listening to???