Acceptable. The beginning was a little slow, as we introduced (or half-introduced) the platoon of characters needed for the story, and I was complaining that I was about halfway through the book before anyone was killed. After that, though, things picked up a little. In true Christie style, the mystery was unsolvable by the reader, especially a modern one that may not be familiar with some of the products and materials available in the early 1930s. Still, parts of the motives and actions were guessable, and the story did move once it got going.
Biggest peeves: people who do things like “I know who the killer is! I’m going to tell you who the killer is! Are you ready? Okay. Here it goes. The killer is splort”. Likewise, Poirot seems to have a rather cavalier attitude towards running around a ship with a murderer loose. Ah, well.