I would consider it to be proto-Romantic, as it was the core work in the Sturm und Drang movement. This is not to demote it in anyway (I actually prefer Goethe to Schiller). Having been more influenced (and, thus familiar) with the later Goethe, I am reminded constantly of his maxim ‘What is Classical is healthy; what is Romantic is sick.’ His later turn from proto-Romantic beginnings toward the Neo-Classical has done a great deal to how I view his impact on German literature. I must also add that no single article (or even a single book) could do justice to these towering figures and their bodies of works. I hope to return to Goethe so that I might write about Werther but this will have to wait till a later date. Thank you for the question.