A science fiction roleplaying game, perhaps the best of its genre ever created. Traveller kept the rules fairly light, kept the science fairly realistic, and didn't require a whole bunch of funny dice to play. The various books and supplements detailed a stupendously large empire called the Third Imperium, which gave just about every roleplayer something they liked, from court intrigue to grunt fighting on the frontiers.

It was eventually replaced by MegaTraveller, the game's second incarnation. While MegaTraveller cleaned up a lot of the mechanical problems Traveller had, it started to take the Traveller universe in directions some of the players didn't want to go - specifically, the emperor was assassinated and the grand, sprawling empire broke up into the space opera equivalent of city-states.

Then in 1993 third game's third incarnation, called Traveller: The New Era, was published. This book wasn't a great success, partly because the mechanics were completely changed and also because the Third Imperium was completely destroyed by a sentient computer virus called (of all things) Virus.

Then the original designer of the game, Marc Miller, tried to recreate what was so special about the original Traveller in a new book called Marc Miller's Traveller (usually abbreviated T4). But this book also had problems - there were an unusually large number of typos and pasteup errors, some of which actually prevented the book from being used as written. The mechanics were simplified from Traveller: The New Era, but still did not even begin to approach the simplicity of the original Traveller game. Several supplements were published for the line, but it sank pretty quickly.

Then Steve Jackson Games got into the act, licensing the Traveller universe and producing a version of Traveller based of their GURPS roleplaying system. GURPS: Traveller (as the final book was called) was considered a step in the right direction by longtime Traveller fans - it was mostly written and edited by Loren Wiseman, an experienced Traveller writer/editor, the GURPS system was much cleaner than the systems of Traveller: The New Era or Marc Miller's Traveller, and the book set up an alternate timeline where the events of MegaTraveller and Traveller: The New Era never took place.

Since then, many supplemental books have been released, ranging from mediocre to staggeringly good (the Scout and Merchant books, in particular, have been widely praised).

As I write this, plans are being made to reprint the original Traveller books (now called Classic Traveller) and Marc Miller is saying he wants to do a T5...

As you can see, despite its checkered past, Traveller is a game that a lot of people know and love and don't want to see die.