Reddit reviews Eifelheim

I am not sure if this would interest you, but Eifelheim is set around this time.

>Father Dietrich is the village priest of Eifelheim, in the year 1348, when the Black Death is gathering strength but is still not nearby. Dietrich is an educated man, and to his astonishment becomes the first contact person between humanity and an alien race from a distant star, when their ship crashes in the nearby forest. It is a time of wonders, in the shadow of the plague. Flynn gives us the full richness and strangeness of medieval life, as well as some terrific aliens.

I thoroughly enjoyed it, it really isn't about aliens conquering earth or anything, it's a good read.

Eifelheim - https://www.amazon.com/Eifelheim-Michael-Flynn-ebook/dp/B000V770AK

Google is scary good sometimes, got it from:
"book with aliens crash landing in medieval times"