Got my Money Site Back

I had a small thin site with an excellent written review that was getting a 10% vistor to conversion rate. Aka 10 sales per 100 visitors to my site.

Just managed to get the site back ranking number 4 or 5 in google first page.

I want to add content to target more traffic and make it more authorative, however the basis of the site is around reviewing a product.

Kind of a dumb question but what type of content should I be adding?

The entire focus of the site is to sell this one product so I dont want to add content that is just going to distract users from that purpose.

Pretend the site is reviewing a "fat burner" product.

Would adding random articles about "benefits of vitamin a" or benefits of "cod liver oil" be beneficial?

Not really sure how to do this.

Think about the questions that people would ask about the product.. For example, if it's a natural supplement one might ask "is it ok to take supplement a with supplement b?".. if its a fat burner product then one might ask if this product is safe with a variety of different fitness supplements, such as creatine or a prohormone supplement. Discuss everything you can about the product and answer all the questions about it that you can.