Xjyuk

I'm looking for a book I read in the early 1990s that is probably a bit older than that. I picked it up in paperback off a used-book rack in bad condition, and it had one of those extra-generic 1980s painted covers, so might have been a decade older. For some reason, when it came back to my mind, I thought it was by David Drake, but nothing I can find from his limited fantasy output matches it.

The basic worldbuilding conceit of the novel is that everyone has a D&D-style "class" and experience level visible to everyone as glyphs or tattoos on their forehead, which apparently appear by magical means; they aren't applied by the people themselves. The glyphs are easy to interpret, for example sailors have anchors on their foreheads, and more anchors means a better sailor. Likewise, merchants all have barrels.

Another interesting detail is that the world is relatively small and organized around a circular river. It's not a canal; there is a current and so forth. However, sailing downriver for long enough will eventually loop around to the same places that were passed upriver.

The plot revolves around a vague conspiracy, which I recall as just "basic economic literacy" without remembering the details. The key point is that it's carried out by a certain character class with distinctive forehead markings that no-one can recognize or understand. Apparently all people with this marking are involved in the conspiracy, so it amounts to an indication that the person cannot be trusted; as a result, they must be very indirect.

The main character is recruited to investigate the conspiracy by some members of the merchant class, because he is a Conan-type superior physical specimen. This is indicated not only by his physique, but because he has a large number of swords on his forehead, more than anyone has ever seen before. However, it turns out that this isn't the whole story; his body is that of a great warrior, but it has had someone else's mind stuffed into it. This is a reader-relatable character who "died in the real world" and then found his real-world personality transferred into the impressive body.

So far as I'm aware it was a standalone book, not a part of a series, despite setting up quite a lot of worldbuilding tropes as I've mentioned.

This is Dave Duncan's The Reluctant Swordsman.

Wallie figured it was fever when he awoke, not in his hospital, but in the body of a brawny barbarian. A swordsman of the seventh rank, Wallie was now the master of a beautiful slave girl and a cunning blade. His mission: to serve a Goddess--even though he had never fought before! Original.

It is a part of a series (a trilogy of at least four books). I happened to have read it several years ago, and remembered the plot points of the forehead symbols and the inhabiting personality from our world.