From the rear cover:
Alien Module 5: Solomani
When the Ancients visited Terra millennia ago, they seeded humaniti among the stars. Those who were left behind were the Solomani and when they finally achieved jump travel, found the worlds around them already populated - it was the Solomani who toppled the Vilani Imperium, established the Rule of Man and bought on the Long Night.
This book investigates the Solomani, their empire, technology and society. Full rules are given for creating Solomani characters and a complete sector is provided in Solomani space to begin your adventures far from the Spinward Marches.
To use this supplement, a Referee will require the Traveller Core Rulebook