From the back of the book:
Welcome to the Journal of the Travellers’ Aid Society, your indispensable guide to adventuring in the Far Future.
Each volume is a treasure trove of information and game additions for Traveller, including adventures, new ships, alien creatures from across Charted Space, philosophical musings on the big empires, histories, different takes on familiar equipment, new vehicles, characters to be met in starports, playable alien races, and much, much more...
Amongst the many articles in Volume Four, you will find:
The Hlanssai, a fully playable alien race from the Vargr Extents
A Travellers’ guide to the Florian League
Siduri Station, a complete starport to visit and explore
The Mainstrider 300T, a new trading vessel for starting Travellers
A detailed look at sensor operations and how to get the best results from unknown blips
Imperial Marine Task Force Organisation