"Brain Plague" is the new hard SF novel by Joan Slonczewski, set in the same future universe as her award-winning" A Door into Ocean" and "The Children Star "(a "New York Times" Notable Book). An intelligent microbe race that can live symbiotically in other intelligent beings is colonizing the human race throughout the civilized universe. And each colony of microbes has its own personality, good or bad. In some people, carriers, they are brain enhancers,...