Incite Insight by Robert New

Linked by a mysterious tattoo, people are dying from their brains melting. A novice detective is assigned to the case. He uncovers an intelligence raising program which he starts working through and it begins transforming his thinking, but the more he learns the murkier the investigation becomes, especially since it appears the program is being used to kill.

Praised as “educational of the human condition” & “smart and imaginative.”