Gunpowder Empire, by Turtledove
The premise of the book is a family from a modern ATL in a primitive ATL, secretly, to trade. The theme of the book is how terrible it is to be stranded in a primitive culture. No problem. The motivation for people to be there is not very realistic. They aren't there to find and retrieve cultivars of fruit trees, or to study alternate timelines, or to pump oil or mine metals, but to buy wheat to ship home to their own timeline. Turtledove just does not understand technology. I mean, I wouldn't even do that as a satire.
Also, he has the locals worried about trichinosis. That's a New World disease. If you have trichinosis, you have syphillis, corn, and potatos.
On the good side, it's competently written and interesting. Too bad he didn't give it a more realistic premise. Anthropology, cultivars, or biopharmaceuticals would have been more realistic. I mean, how much would you have given for giant syphillum, the natural abortifacient that the Romans had that went extinct around the end of the Roman Republic?