City-State of Tyr, by Walter M. Bass, is, fortunately, not that other shoe, but I can definitely see its shadow. There's a whole chapter, called "Personalities," that is largely just character sheets for important figures from the novels.
King Tithian, who "it is doubtful that any PCs will ever personally encounter" gets his psionic powers listed as "current level of ability unknown." That's a big red flag. The book is supposed to be an objective reference to the City-State of Tyr. The way that facts about the city and its residents become known is by being written down in books exactly like this one. So how can his "level of ability" be "unknown" when anything you write down would, by definition, be the true and correct answer? Unless, perhaps, you're holding something back. If maybe the rpg supplements don't have the authority to establish new canon, but are merely supposed to report on it. If the novels now take priority.
It's a sobering thought, but luckily, we're not quite at the worst case scenario. It's not like Pendragon where the player characters sometimes feel like intruders into the canon. There's no scenario that's like "The PCs will attempt this and fail because Rikus and Neeva are going to come along and solve this issue in Book 4 of the series." City-State of Tyr is mostly a useful setting guide with only the occasional bit of frustrating bread-crumbs towards the ongoing metaplot. The king is missing, because he's left the city to participate in something called, "the search" (the quotes are in the original text), and it's kind of a problem because he's supposed to be a major part of the civic life of the city, but also it's not something that bears further exploration, because that's literally all we know about it.
I think, if you're going to use this book, you have to keep it low-level and away from the palace. Stick to the bars and inns. . .
Yeah, that's right. Just like In the Cage: A Guide to Sigil, the city of Tyr has a thriving hospitality industry, with plenty of places to meet shady contacts and discuss vaguely disreputable "adventures." And while it's well-suited to be a place where the PCs are just passing through, it also has plenty of local color (like a pottery shop, a perfume store, or a jeweler with a complex backstory) that allows it to serve as a permanent base of operations.
Also, if we give it a mulligan on Tithian's mysterious bullshit, it's a unique and interesting location for some really intense political games. The old sorcerer king was recently assassinated, the slaves were freed, but the rest of the social order is largely in place. Most of the templars still have their old jobs and the nobles still own most of the land (about 20% of the farmland outside the city was redistributed to newly freed slaves as part of a whimsical homesteading scheme). So what you've got is a king who is a reluctant reformer, who had to be pressured into adopting progressive policies by his Council of Advisors (many of whom were responsible for the assassination that put him on the throne), and yet because those machinations are behind the scenes, the masses only see the results and reward him with immense popularity. Versus an educated hierarchy of bureaucrats and administrators who are emblematic of the old regime, and thus a tempting target of vigilante violence, who therefor must rely heavily on the new order for protection even as they undermine it with corruption. Versus revanchist nobles who have no particular love for the old king, but who took a major economic hit from the revolution. Versus radical progressives who want to push for even more equitable political change. Versus a lumpen proletariat of newly freed slaves that the system is ill-equipped to absorb, which doesn't so much as have an agenda as a dangerously volatile anger that may find itself directed against any number of perceived outrages.
The city is ready to burst, and PCs are poised to be at the center of it. In order for it to be a truly great campaign book, it would have to dial in a bit more on the factions, their motives, and their methods, but the broad outline is there. And the physical geography of the city itself is well-covered. And the book describes clothes! Overall, I'd say that it's a good addition to a prospective Dark Sun campaign, even if it does sometimes fill me with a metaplot-based foreboding.
Ukss Contribution: There's a bar, called House of Fingers, that is a sort of neutral meeting ground for Bards. The book got a little carried away with the idea that Athasian Bards will sometimes moonlight as assassins and wound up making the Bard bar into a really grim Assassin bar, but as far as grim Assassin bars go, House of Fingers is memorably awful. "The thousands of [severed, humanoid] fingers that line the wall create a surreal and macabre atmosphere."