On one hand, it's HBO so you know the production values will be highish for a cable show, on the other than, it's HBO, so the sex scenes will be borderline softcore porn.
Wait, wasn't there supposed to be a negative in that train of thought?
The books were so thick at 1000+ pages and had so many plotlines going on at once, it'll be a really long time before they get through what's there. I doubt a season per book would cover everything, depends on episode length and how many per season.
Plus, figure he didn't go into great detail on battles very often, but there were plenty of them to use as filler. A few lines of action can turn into quite a bit on screen.
Anyway, should be really good. HBO has a great track record for TV series.