"a lowly opinion is worth about as much as a great one. an uneducated one on the other hand..."
basically your opinion is as worthy as anyone else's, so just write it down. it's not about your argument that you get graded on, it's about how you do it. support your opinion and make sure it's well founded on, that you have evidence and ground for your belief. if you didn't even read the article and are trying to express your point- it's a little hard since you don't even know what your argument is. cite resources that add value to your opinion, other articles or journals that may support it, you can even use historical examples if applicable. another that's becoming more looked at now is personal examples, what exactly have you gone through or experienced that made you think this way.
don't be un-original and think that the book already has your opinion, it's SIMILIAR. use the book as support for your own stance. finding it acceptable doesn't equal exactly what's in your mind. the best way to avoid plagiarism is using their writing as a launching pad for your own paper, if he uses a really catchy phrase or metaphor that you really like you can quote it (cite that quotation).
good luck