Title: The Last Master
First published: February 1984
Description: From back cover Tor paperback February 1984:

ONLY AN R-MASTER CAN SAVE US FROM THE R-MASTERS

Etter Ho took a gamble when he took the R-Master treatment.  Sometimes it turns the subject into a supergenius; more often it turns him into an idiot.  That's what happened to Etter's brother when he decided the treatment was his only hope of winning the woman he loved.  Then Etter decides to try the treatment himself, and, if he wins his gamble, to use his new powers to discover a treatment for the treatment.  Etter comes up lucky, but with his new-found powers, the problem of curing his brother and all the others who tried and failed fades before the greater problem: he, Etter Ho, and his fellow R-Masters are the greatest threat the Human Race has ever faced!
Subjects: Fiction, Brothers, Intellect, Fiction, science fiction, general, Fiction, general
Places: Hawaii