The Original Agatha Christie: Poirot series in order as best I can. Currently only on book 2, Murder on the Links.
I've also been reading a random series I found called: Bernie and Chet. It's a detective/P.I. novel mystery series, but from the perspective of the dog-partner. It's pretty interesting how the author handles situations and divy-ing information the story progresses through the eyes of a dog. A much simpler read than Poirot, but still a page turner although somewhat predictable.