Brightness Reef (The Uplift Trilogy, Book 1)

Millennia ago the Five Galaxies decreed the planet Jijo off limits. But in the last thousand years six races have begun resettling Jijo, embracing a pre-industrial life to hide their existence from the Galactics. Overcoming their differences, the Six have built a society based on mutual tolerance for one another and respect for the planet they live on. But that has all changed with an event the Six have feared for hundreds of years: the arrival of an outside ship. Author David Brin has returned to his popular Uplift universe in this, the first book of a new trilogy.