I haven't watched the show or read the book yet, but I sometimes suspect with these Christie adaptations that they really want to do a new story, but they don't have the balls to just do that.

Not unlikley! I read someone involved with another Christie adaption saying they "have" to do chnages as Christie is so well-known, but I think that is ridiculous. I don't watch an adaption to see how they have changed the original story, I watch it to see how they have interpreted it. And people who haven't read the original won't know it's changed anyway.

Why Didn't They Ask Evan? was so good! And very faitgul to the book.

Okay, I'm back having read the book and watched the first 30 minutes of the show, and I'm already annoyed at the changes because they aren't necessary, and they aren't adding anything to the story. Like, that plot is perfectly constructed on its own, and the characters are interesting and could be expanded in interesting ways. So why on earth make all these changes?

Yes, exactly! Why? I stuck it out to the end, but I won't ever re-watch it.