The Further Adventures of Sherlock Holmes: The Martian Menace - Eric Brown

A new addition to the Further Adventures of Sherlock Holmes series from science fiction and crime author Eric Brown.
A DEADLY PLOT
For the second time in human history, Martian invaders occupy planet Earth. After a common terrestrial virus thwarted the first deadly invasion, another Martian armada arrived six years later to make peace. Now, mankind enjoys unprecedented prosperity due to the aliens' scientific wonders and technology, and an entente exists between the two races. But when Sherlock Holmes and Dr John Watson are called upon to investigate the death of an eminent Martian philosopher, they unravel an intricate web of betrayal and murder that leaves no one - human or Martian - beyond suspicion.