This was a desest based campaign world with an Arabian flair. From what I hear, it was a very good world. TSR disagreed. It is the only campaign world, other than the new Mystara, not recognized (with its own page) on the TSR web site. It is also discontinued.
This world is based on a series of books by Fritz Leiber. It is very simmilar to the generic, Greyhawk, and Forgotten Realms worlds. TSR has not released anything for this world, and I don't expect that they plan on releasing too many more, but the Wizards of the Coast might do otherwise.