I watched this over the weekend solely (at first) because it has Richard Armitage in it. I quickly became hooked on it and binged the whole thing in two days. It's very edge-of-your-seat television with lots of twists and turns. And it boasts an amazing cast. In addition to the aforementioned Mr. Armitage, it also stars Siobhan Finneran, Hannah John-Kamen, Jennifer Saunders, Stephen Rea, and Anthony Head just to name a few.
I've also ordered a used copy of the book. I'm eager to compare the two. I know there were a lot of changes made between the book and the show.