For me, one of the great joys in Traveller is visiting other worlds, and whilst I enjoy inventing them it is always useful to have a few ready-made ones to hand. So a series such as the one that this is the first example of is a boon to all busy Referees!
It provides a comprehensive run-down of a single planet, ready for your intrepid Travellers to... well, do what they like on. It's not just a UWP (Universal World Code) or a map of the place, although those are there, it's not just a few lines of description that you have to build on but a whole wealth of information that starts to spawn plot ideas even as you read through it.
Different locations for those who wish to venture beyond the starport, local NPCs to deal with, even the wildlife, governance (a lot more than a bald government type code), typical vehicles and more, rounded off with a collection of plot seeds in case your imagination has run dry.
Watch out for the next one... meantime, my players may want to look out for Ubar popping up on their star charts!