So its alternate history but based heavilly on historical events.Watched an episode and a half of shogun and really like it so far.
Very well made, good to look at. Plot is a very interesting piece of history.
Broadstrokes this is what was happening in Japan at the end of the Azuchi–Momoyama period going into the Edo Period.
Clavell departed from actual history enough that he renamed all the historical people with new characters but its clear who their analogues are.
So yeah its interesting because you do learn what was going on in that part of history in terms of politics but don't really learn anything in terms of how events transpired.