I've only seen two episodes, so this is a somewhat uninformed review. Oh, and I haven't read the book, which probably helps to enjoy the show as it's own creation.
It's important to note that Ridley Scott is a producer and his most recent film Robin Hood, shares quite a resemblance to the general story and setting of Pillars. (Side note; the opening credits are exactly the same). If you've seen Robin Hood, then you get the Monarchical, religious complications as well as the bleak, foggy, dark blue world backdrop of old England.
I was expecting a more fantastical, mythical world, but this series is pretty grounded in reality so far.
The show's greatest strength is the actors. You can't go wrong with Donald Sutherland and Rufus Sewell in a TV series. And Ian McShane is always great, especially when he's playing a dark character.
Might not blow you away, but unless the show takes a nosedive, it's definitely worth watching.