The second book in the Faded Sun trilogy, one of my all time favorites. If you like CJ Cherryh, or if you like anthropology, sociology in a future setting, you won't be sorry to read this series.
From the publisher
The golden-skinned mri warrior Niun was heavily sedated and had been for some time. Teams of scientists and physicians, intent on studying an alien species, preferred having him drug-dazed - totally helpless in a place that echoed with hostile voices. One human felt differently and was struggling to make a decision of his own. Sten Duncan came to visit Niun and Melein every day. He was immeasurably grateful for their continued survival, yet painfully aware that the mri would rather have died than exist as they were. Sadly, Duncan would remember this brother and sister as he had first known them: he had crossed a world with them and their fierce dusei - bearlike, semi-sentient creatures devoted to the mri. Together they had endured many hardships...and the horror of seeing an entire mri population wiped out in a single act of treachery.