I finished the series in English, the official translations aren't too bad but I do think you need to adjust to enjoy the tone of the novels. They're often dark but at the same time don't take themselves as seriously as English fantasies are prone to. The Tower of the Swallow was my favorite one and I can't tell if that's because the unofficial translations are better or it's just the best installment of the series.
I'm almost done with the game, will probably write up my thoughts in an EoFF blog post, I've littered this thread with my impressions too much as it is