It started quite slow, understandably perhaps, as the scene was set with a coup in a small middle Eastern country and the introduction of the characters in an elite girls' boarding school in England. The teachers at the school are then systematically murdered as a would-be thief searches for a cache of jewels that was inadvertently smuggled into England because the pilot of the dead heir of that small middle Eastern country hid the cache in his niece's belongings. Poirot, surprisingly, doesn't figure into any of this until the very end when a 15-year-old girl has already solved half of the mystery.
I wouldn't say that this is among the best of Christie's work--I figured out half of the puzzle before the answer was revealed, and I suppose I wasn't surprised that the character that I disliked the most turned out to be the killer. But I didn't find the title quite apt, the killer blended quite well with everyone else thus it should have been A Wolf in Sheep's Clothing.
If you've never read Agatha Christie before, I suggest beginning with And Then There Were None (originally published as Ten Little Indians). It's a classic in and out of the mystery genre. Besides, if you read it during a dark, stormy night, you might be able to scare yourself silly.
