I did search for this, but couldn't find it.

Many of the books I read have review pages dominated by reviews of audiobook editions. I've seen books given low ratings solely because of the narrator/narration, with no review of the actual content, and in the book I'm currently reading, the vast majority of the reviews focus on that narrator and/or narration in a positive way.

I'm sure that for users who read exclusively or primarily via one medium, being able to filter reviews to only show that medium would be a great enhancement, filtering out reviews that are irrelevant to that user's reading experience.