"Murder on the Orient Express" by Agatha Christie is pure murder mystery. It starts off innocently enough when Mr. Ratchett is found having been stabbed in his sleep, but the case quickly becomes more and more complicated. Hercule Periot has to struggle to find the true culprit in the mystery that gets more tangled by the second.
The characters in this book are all rather good. While none of them have outstanding depth, they are all interesting and well defined. Hercule is, of course, the standout. His methodolgy is always fun to read. The suspects cannot be discussed without getting into spoilers. Even the victim is interesting to read about.
Most readers will probably know the twist of the book (which I will not be spoiling). Still, it's wonderfully set up, and almost every piece of evidence contributes to the climax in some way. New evidence is constantly presented throughout the story. At times it was a bit hard to follow, but I'm notoriously bad at following along with mysteries.
Nothing in this story is particularly deep, but it doesn't need to be. It's just a captivating mystery story. One of Agatha Christie's best.