Differences in online reviews between different communities: An empirical study on Amazon and Goodreads

Many book buyers rely on online book reviews to make their purchase decisions, particularly the reviews on Amazon and Goodreads. However, multiple sources claim that there are notable differences between Goodreads and Amazon reviews, which can be confusing for readers. Here, we examined whether such differences exist between Amazon and Goodreads in average ratings and the number of raters, based on quantitative data. In addition, we investigated how these differences vary by book genre, specifically fiction and nonfiction. We hypothesized that 1) Goodreads has more ratings, or raters, than Amazon for the same book, 2) Goodreads has a lower rating for the same book, 3) the average difference of the number of raters between Goodreads and Amazon is larger for fiction books, and 4) the average rating difference between Goodreads and Amazon is larger for fiction books than nonfiction. We analyzed data collected from both online platforms, including ratings and number of raters of 400 books, with two-sample t-tests and regression analysis. We found that while ratings on Amazon were higher than those on Goodreads, the number of raters on Amazon was lower than those on Goodreads. Our findings suggest that the overall rating and rater differences between Amazon and Goodreads are significant. Additionally, our findings indicate that rating and rater differences are larger for fiction than nonfiction books. These findings will help buyers and practitioners in the book market correctly understand consumer reviews on online platforms and the potential quality of books.