If the series continues to follow the books it will be pretty good. England at the time is close to defeat and Uhtred plays a significant role, helping King Alfred. Bernard Cornwall always has a twist. In Sharp it was having an officer raised from the ranks that others didn't see him as a gentleman and therefore an officer. In Rebel it was a Northerner joining the Southern cause and again not being quite accepted. Here, Uhtred is never really trusted as he is a pagan (being raised by Danes) among some of the most god-fearing people of the time. It makes for an interesting clash of personalities.
However, there are some glaring mistakes. The interpretation of a shield wall is all too wrong. It may be that this first adaptation was unique to the first battle. In the scene the Danes form a three wall tall shield wall with no gaps and men crouching at the front to cover their feet. This is fine against arrows, but against another on-foot army it wouldn't work. You simply wouldn't have the numbers and the enemy would just outflank you.
Let's hope that the Last Kingdom changes battle tactics in future episodes, otherwise two armies facing each other in a shield wall would be very dull indeed. Otherwise, a very interesting programme.