What a map cannot tell you
Some roads look nothing on paper like what they turn out to be.
A map will give you the shape of a road and the distance between two names. It will not tell you that the surface changes at the pass, that the wind arrives from the left after the second bridge, or that the village you were counting on closes early.
I have ridden roads in this country that look, on no map, anything like what you meet in reality. That gap is not a failure of the map. It is the reason to go.