I really enjoyed the book, but wasn't thrilled with some aspects of the movie. For me, it would have worked better if they didn't use the same actors in the different story lines. I realize that in the constraints of a film, it might be harder to grasp the linkages between the stories if they had used different actors. However in this case I didn't like some of the makeup and accents, some of which just felt hokey to me. Also, in the book, The Ghastly Ordeal of Timothy Cavendish was horrifying to me, where as the film version was goofy.
Warning: Spoiler! (Click to show)
It's almost as if the version we see in the movie is not the actual story, but more of lighthearted retelling or perhaps even a movie version of itself (like the one that Somni watches in the distant future, which we see clips of in the movie and are clearly not the same). I felt like the other timelines were trying to be true to the soul of the book, where this segment came off as allegory.
Obviously anytime you see a movie after reading the book version, you're asking for disappointment, and I accept that my opinion is skewed because of that. There are parts of this film that worked very well for me, but others just didn't, and those parts that didn't really left an impression. Have you ever been to a play that you really liked, but found just one or two miscast parts, and it was so obvious that when you walked away all you could remember was how awkward those parts were? I guess that's what happened to me here.