"No mystery is unsolvable. Truth smiles upon me!"
I feel it very necessary to say, I have not yet read anything written by Agatha Christie. I have no doubt that the original books were superior to this adaptation, and I can tell just from watching the show that the stories had an excellent source material. The main question for Christie fans will probably be, "How much adaptation decay is there?" I cannot answer this, only talk about how I felt as someone who was experiencing everything in this show as fresh and new.
In part to provide a common link between Miss Marple and Hercule Poirot, the lead detectives of our story, and also in part to give children a character with which to relate, we are introduced to Maybelle West, a 16-year old girl who is learning how to become a detective. Maybelle also comes along with the unfortunate companion of Oliver the duckling. Maybelle, when she's not being a horrible brat to her father, is mostly smiling and friendly and vapid. Fortunately, she doesn't intrude on the established stories very much. She assists Poirot and Marple, but I often times forget she is there. Oliver is harder to ignore, because when he pops his head out of his basket, the camera is squarely on him until he disappears. Oliver gets far too much screentime for a creature with zero purpose other than to be adorable.
If like me you haven't read these stories before, don't think you won't be fooled just because this is a "kid's show." Yes, sometimes they add in extra clues, but for the most part these are riddles that will challenge an adult mind. Sometimes I correctly guessed a culprit and reasoned through it, and sometimes I didn't. That's probably the genius of Agatha Christie shining through.
At the heart and despite all the trimmings, this show is classic "whodunnit," with an ample side dish of "howdunnit." Marple and Poirot are both the kind of people who prefer to solve a crime with deduction than following breadcrumbs. So, instead of a crime story where breaks and new leads in the case are handed to us, we as viewers have to slowly gather facts and read suspects. There is almost zero action in this show, and that is just fine, because it kept my brain chugging along. The suspense is good enough to cut with a knife.
While the animation screams "low budget," it doesn't really hamper the show as there's no action to be animated anyway. A positive and surprising tip of the hat should go to the soundtrack, which I felt heightened the show quite a bit, including the OP. It's more than I would have expected for a show of this type.
Despite the simplicity of all the main characters, Marple and Poirot included, and the younger audience wrapping, there is a distinct satisfaction that I got from watching this show and trying to figure out how the bad guy did it, whether I'm right or wrong. Some of the cases are brilliant, and it's easier to watch four episodes than it is to read a novel (if you're the lazy type). You do not need a background of reading Christie stories to appreciate the mystery. The show actually has made me want to go to the bookstore and check out some of Agatha Christie's other work. So while certainly not perfect in translation, the core of this anime was solid enough for a fully grown adult like myself to enjoy watching it.