From the publisher:
An entire subsector at your fingertips!
Subsector Sourcebook 1: Cascadia compiles our first 12 Quick Worlds sourcebooks AND adds 8 more unpublished worlds to challenge and entertain your characters.
Made with the busy Referee in mind, this book can provide the spark for multiple adventures. Use Cascadia as a whole subsector to expand your existing campaign! Or simply use this book as a handy central source for 20 Quick Worlds to use individually as you see fit!
From the introduction:
This book is intended to provide a Traveller Referee with a subsector full of adventure for his or her players. It can be used as an adjunct to an existing Traveller game or be used as the basis of a new campaign.
This book, as it is presented, is largely setting neutral. That is to say, it is not connected to any existing setting that has been so far produced for Traveller. A Referee can, of course, in the privacy of his/her own home, add this subsector to any number of existing settings or sectors. Alternatively, it can be used simply as it is presented and provide a useful background. Indeed, it is our hope that we can save Referees a certain amount of preparation time by providing a subsector upon which he/she can base his/her storytelling.