The Borderland is a sourcebook providing the Referee with a semi-isolated ‘sandbox’ within which to set a Traveller TTRPG campaign. In printed & PDF format.
www.mongoosepublishing.com
It came out last year and it details two clusters in the Borderland Subsector of the Trojan Reach. Probably the most well known of these worlds is Tech World but it includes ever system In that Subsector except Bryni
I like Borderland because it gives a good framework to build on including the UWP for all the worlds in each system while still giving the GM lots of room to customize