Are the game and the manga based on the same premise which is "The Saga of the Greenlanders", where is told (among others) the story of Leif Eriksson and Thorfinn Karlsefni expedition toward a new land they called "Vinland"? Yup.
Is the game in any way affiliated to the manga, a plagiary, a remake, or a cash-grab? Absolutely not.
Should anyone read the manga? Yes, absolutely.
Should anyone watch the anime? I don't give a fuck, I don't like anime adaptations.
There, that should recap my view on the subject