Among the best action, humour and seriousness mix the Shônen Jump has produced.
The original chinese classic novel settings benefits greatly to this manga based on the japanese contemporary novel. It gives it also a non-archetype shônen hero and a multitude of characters who will NEVER be useless (among them, some very charismatic ones) all distinguished thanks to the beautiful art of the mangaka.
Don't think it will be boring because the epic story is very old, no! the mangaka is there to make the war appealing through those immortal taoists and monsters/yôkai battles in pure action shônen style. He adds also his own predilection genre, the sci-fi, to explain the superior abilities of those reclused people who are clearly far away from the poor chinese folk in a lot of domains. This leads obviously to a lot of humorous anachronisms who still never feel forced or out-of-place.