Shinkai, as always, wrote a cliché script for the film, and in the novel it is the same thing, during history it is possible to notice a significant amount of errors in the plot, but it is useful in general.
The film is clearly the best way to consume this work, the excellent visuals and animation distract you from the decadent script.
I recommend it if you really loved the movie and want to have something to remember it even more, but if you are going to read it just to have a pleasant moment I don't recommend it.
Note: it has exactly the same thing as the movie, you will not be losing or adding anything to your experience.
