I'm slightly judging myself on this one as I really should have read the book before now. I think I might finish the first season and then pick it up.
It's a pretty good series, with fairly interesting plot, but it certainly feels like an adaptation of a book. The tight focus on a rather minimal number of characters feels a little off in a programme which has such a wide premise. I'm sure the purists wouldn't have been happy, but I would liked to have seen a much wider scope of characters and plots.
Still, the set dressing is excellent, and it does all feel like a consistent world. I just wish they'd done more with it.