The premise is odd, but the result is spectacular. Michael Kitchens' DCS Christopher Foyle is smart and witty and commands respect without even trying. The plot twists are exciting if a bit contrived (I truly hope Hastings doesn't really have the murder rate depicted here!), and the way that the crimes and pursuits are integrated into the background of wartime England keeps everything very relevant. The balance between drama and levity is perfect. Just when you think things are just going to be dour and boring, you are rewarded with a subtle, dry, and witty comment by Mr. Foyle. He is the main reason I keep watching, but the supporting cast is fantastic as well. Honeysuckle Weeks' Sam Stewart is awkward in a very charming way as she drives the Detective Chief Superintendent around Hastings, helping solve crimes in her own way. Anthony Howell's DI Paul Milner can come across as dull, but he has more depth that is revealed as the show progresses. I sometimes feel like this show was made for me haha! It is very British in every way, and ever since I finished Downton Abbey I feel I have to have at least one British show in my rotation at all times. This is one of the best.
I've read many of the comments here and I realize that what people do or don't enjoy is highly subjective (except, maybe, She's the Sheriff - that's just awful). I try to take shows and movies for what they are, not for what I want them to be. Essentially, Cuoco's character Cassie is Penny from Big Bang if she hadn't met the guys and settled down. I quite enjoyed watching Cassie being a hot mess. Sure, she went out of her way to do extraordinarily stupid things that got not only her but other folks into trouble or worse, but it was entirely within the bounds of her character. The show is quirky, funny, dark, disturbing, very unrealistic, and keeps my attention through each episode. It certainly isn't for everyone, but I, for one, found it delightful.