First of all the the music in the movie (especially when Veronika plays the piano) is very moving and really dragged me into the emotions of the scenes. It is so intense as if Veronika's inner world and feelings were my own.In my opinion Sarah Michelle Gellar did a great job conveying the personality of the character to the viewer.
Many people have read the book and I think that many will find the adaptation quite successful. As with other books made into movies, it is not as detailed as the original, but it is surely as intense and emotional.
As for criticism, somehow I find the role of the doctor somewhat secondary, there wasn't much interaction between the two of them. I was also a little surprised at how abrupt the movie ended at first, but as I think of it, a 30 minute ending would do more harm than good.
And the message is what is the most important part, it is something that all of us should be reminded about. And in contrast to other films with great messages, this one has a rich atmosphere that compels you to watch and watch and watch.
I guess more of Paulo Coelho's books will be made into movies, but I hope the adaptation is at least as good as this one.