From the back of the book:
"The original setting for Traveller, the Spinward Marches are an area of space right on the edge of Imperial territory. This sector is one of the most volatile to be found anywhere, with mighty interstellar wars a key part of the region's history and with no clear winner - yet. As a place of adventure it is unsurpassed within Imperial space, with enough 'special interests' to keep any group of travellers profitably employed for many years.
The Spinward Marches contains a history of the sector, with all major races and governments found there covered, allowing a Referee to include political machinations in his campaign. It also provides details on the various corporate entities that operate within the area, all of which ruthlessly compete with one another, often using violent means to ensure the bottom line will remain profitable.
All sixteen subsectors are featured, with detailed descriptions of many worlds found within them. This book offers a great reference for all campaigns and within its pages opportunities for adventure are both exciting and almost limitless.
Welcome to The Spinward Marches!"