Finished this one and I liked it. I watched the movie and knowing the end beforehand did ruin the experience a bit but I still enjoyed it. So many film/TV adaptations make a mess of the source material,but Suchet somehow made the episodes just as good,or sometimes even better than the books! Which is really saying something. Every single character in the book is so interesting, that was what I enjoyed the most about it. Once I got to part 2, I was very engrossed. I think the author did a great job at giving us characters that were believable, along with characters that you knew were hiding something. I loved the time period, I loved the picture of the train and I was so easily able to picture the scenarios. I think what I liked most about it was the plot twist at the end and also how well thought out the book was. I bet you if I were to read that again I would notice things, and if I were to read it a 3rd time I'd notice even more. It was so in depth and I really enjoyed reading. Sometimes it seems like there's moral standards that everyone agrees with, but we see how it can be interpreted differently amongst everyone and sometimes the standards are strict or flexible in their perspective.
Having read lots of Sherlock Holmes books, I liked Poirot being more relatable and more human.
I'm not sure how I feel about Poirot letting them all go free. It's true that Ratchett (Cassetti) was a monster, and that there wasn't any hope for the justice system getting him, but it's still a group of people coldblooded enough to plan someone's murder in advance, and enter one by one to stab an unconscious (or dead) man.