The best answer I can give to this question, whether it is about this book or my next one, is that while love factors greatly in the story, it is much more than that. No, in my opinion To Miss the Stars is not a romance, if you want to try and pick a genre. It is more about a man and his journey back to himself. Again, love is a factor but not only romantic love. There is his love for his sister. There is his love for Emma, to be sure, and hers for him. But, there is also Willian's love for Emma, if you look for it. There is love of the world around us. And, there is pain and loss. There is transgression and forgiveness. There is introspection and enlightenment.
The best description I can give for To Miss the Stars does not fit in any specific genre and that is that it is a life story.