The first season of Guilt is one of the most interesting, tense, and well-written suspense shows in recent times. It's full of intricate, well-crafted twists and turns, characters who feel like real people, side-plots that come together in wonderful ways. The acting is superb, especially Jamie Sives and Emun Elliot, but all the others are good. All in all, it makes for perfect binge watching.
The second season doesn't work nearly as well as the twists and turns that make the first so effective become laborious, complex, and eventually, way too hard to understand. By the third episode it's almost impossible to understand every character's motivation because they've all been switched and changed so often. The ending is nearly incomprehensible. And as good an actor as Mark Bonnar is, the camera tends to focus on him for interminable amounts of time, almost as if his face is actually part of the plot.
So the advice here is, indulge in the first season, skip the second. Apparently the third is in the works, and with luck, the show's creators will revert to their original intentions and pretend the second season never happened.