I guess you've sort of already answered this but I've only watched the show, still worth reading the books?
In my opinion yes. Books and Movies / TV both have there positives but books can always go more deeper into the characters and motives. Plus there are no time limits or budget you have to fit the story into. GRRM takes full advantage of this. This is also the negative side of the books. GRRM wanders all over the place.