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???
Keith made the blueprint for MF DOOM. 

