Back to the dawn of Discworld and the adventures of Rincewind and Twoflowers. this one's a novel, not a fix-up. spoilers for the first ahead.
Starting with the observation that the two of them, having fallen off the Rim last book, find themselves unceremoniously dumped in the Disc -- the Spell that had leapt to Rincewinds's head from the Octavo. Prior to this, the wizards of the Unseen University found the Octavo, the book the Creator left behind, acting up. The wizards try to retrieve the Spell. An ominous red star glows in the sky. Rincewind refuses to talk to trees even when they talk to him, and his and Twoflower's escape from wizards involves landing on a rock on the middle of a cloud.
Levitated by a druid, who's taking it to fix a circle. There, they witness a human sacrifice ceremony and are fortunately rescued by Cohen the Barbarian. When Rincewind gets a good look at him, he is greatly surprised, until he remembers that the tales were what his grandfather told him; Cohen is, in fact, quite old.
The rest of the tale leads up to ominous happenings under the red star, including Rincewind's meeting trolls and learning that they often come down with bad cases of philosophy, a dwarf who says that stars never hurt him, he wished he could say the same about people, Rincewind's dreaming of being in the Octavo, a little shop that wasn't there yesterday, Twoflower's means of determining what's dangerous, things from the Dungeon Dimensions which make demons look nice, and much more.
Still in the wild and wooly state. I suspect, myself, that being a sword & sorcery parody helped keep the invention up. Epic fantasy tends to go for more world-building and so orderliness.