What Are These
Dungeons and Dragons had a series of thin books that described various locations in its default setting. The Grand Duchy of Karameikos is used for example adventures in the Expert rulebook. The Kingdom of Ierendi showed up in Lathan's Gold. And a quick internet search shows that the Emirates of Ylarum are original to the book.
In terms of old-school supplements, these are the real shit. The covers are gorgeous in that mid-80's overwrought fantasy way. And you can bet your life that all the ladies are staring sleepily into the distance while having implausibly deep cleavage and the men are all doing heroic action poses with lovingly detailed fantastic weaponry.
The back covers of Karameikos and Ylarum both promise a "complete historical, economical, geographical, and sociological overview" of their respective areas. Whereas by Ierendi, they'd mellowed a bit and focused more on pitching the adventure. 1987 must have been a very busy year at TSR.
I think the trickiest thing about tackling these is that they are from before the time when their brand of fantasy became boring. Like, the Grand Duchy of Karameikos looks like peak D&D fantasy. I'm expecting heroic knights, rampaging goblins, and aloof wizards. Maybe there will be some mysterious elves that live in a forest and some taciturn dwarves that live in the mountains.
Ylarum looks like it's going to be benignly racist in that old-school orientalist way, where the author is really enthusiastic about the subject matter, but engages with it through a colonialist lens. Though to be fair to the author, this impression comes mostly from the cover, which feature two men in Keffiyehs, with covered faces, a harem dancer, and a beautiful woman with a veiled face. The rest is just an educated guess.
Ierendi is harder to pin down, at least from the book's cover. It's the one I'm most optimistic about, just because it gives off a purer sword and sorcery vibe than the others (though, the phrase "psychotic natives" appears on the back cover, which is never a good sign).
Despite my cynicism, I'm prepared to be surprised by any or all of these. The advantage of predating the genre it created is that there's still room for the ideas that got dropped in the process of working out the common denominator. The D&D rulebooks themselves were filled with all sorts of bizarre ideas that were largely forgotten. Here's hoping the setting books are early enough to share that sense of experimentation.