First a technical note: I bought this book for the Kindle and the attached illustrations came through (unlike the free version of The Mystery at Styles). So that's that questions answered. :)

Moving onto the book now... This is the very first Miss Marple novel but well into Christie's writing career. There's definitely a difference. Just in matter of scope, Christie juggles far more characters and sub-plots and blind alleys than in her first book. I also felt like there was more confidence in her character-drawing. Not a depth necessarily, but a more deft touch in teasing out various character types. Miss Marple talks about classifying people into types and how that ability grows more refined as you work at it. I'd say Christie had been working at it.

I have no idea if this is related or not (I suspect, yes), but this book was... a little more sour in its view of people than "Mystery at Styles". And a little less humorous as well. When I was a girl I preferred Miss Marple, but based on these two books, I think now I'd rather hang out with M. Poirot.