I have to admit I liked the series, mostly because I really enjoyed Jenna Colemen from the Dr. Who days - she was great then and played well here, except for the murder part.
I will say that both married folks have deep-seated mental issues from unpleasant, though not tragic childhoods, (far worse parents exist), and I believe there are crimes that can be committed that might warrant injury or death, especially in the spur of the moment (catching ones spouse in bed with another, etc.). However, what the wife did was plan out the murder of her husband. Legally, that is 1st degree murder, in any state, and isn't likely to be justified by infidelity, which was the only crime committed, when she started planning the murder.
Plus, frankly, no one is worth going to jail for. I guess for some, the satisfaction of hurting or killing someone who cheated on them might appear to be worth it, while being put to death by society, or spending the rest of ones life in jail, might allow for time to reconsider.
I also found it interesting that she took him right back the first time and he refused to let her go, despite clearly continuing to cheat on her and possibly intend to leave her at a later date, with a lot more pain for all concerned.
Those realities aside, the series was a lot of fun, well-acted, great backgrounds (amazing), and was fairly high-budget all the way around. I enjoyed it, if for Jenna Coleman and the backdrops. Good stuff.