From what I gathered they had to leave a lot of things out. Impossible to mention everything.
What's more, Woo based his film on the actual historical events not the 14th century novel and also developped some characters like Zhou Yu's wife or Princess Sun so as to make sub plots more attractive to any viewers, Chinese, foreigners and those who don't know anything of the Chinese history.
I think the intention wasn't to paste the book on the film.
But to show how Chinese are smart and refined. I really liked the battle of wits in the film. As much as the battle with weapons. Plus Woo shows that Chinese are close to nature, animals, have huge talents for arts, etc...
Is the film released in Holland yet, Pieter?