I apologize if this has been asked before. Is there an especially good resource to read for either world building or roleplay for a Dungeons and Dragons campaign?

I know in theory any history book dealing with the Middle Ages or Renaissance would be good. I guess what I want is a focus on how people lived, what technologies such people used and what peoples lives were like (with maybe a focus on the more interesting traveled people, soldiers, merchants, etc). Learning about the ways people did things.

I would say the less specific the better but learning particulars about a specific culture might lend some unique roleplay flavor. Witcher 3 seemed to have that going for it.