(Not) All Reviews Are Helpful:

The present study aims to analyse the concept of consumers perceived diagnosticity in online books reviews in order to give an overall view on the effects of reviews on perceived helpfulness and on consumers decision-making process about the purchase of a book. The sample includes reviews posted on the webpage of five best sellers on Amazon.co.uk. The paper analyses the relations between stars ratings and helpfulness votes in order to confirm existing theories proved in other economic sectors, such as positive bias and negativity bias. Then the research focuses on the written comments, both on the themes covered by reviewers, that are mainly regarding the content of the book and the author, and the length of the reviews, that does not clearly affect perceived usefulness of reviews. Eventually, the study explores the relationship between the date when reviews are posted and the perceived diagnosticity of these reviews. It discovered that reviews are affected both by early birds bias and winner circle bias. The subject of the research required the employment of a mixed method due to the necessity of confirming actual theories about the relationship between numerical data and diagnosticity and proposing new hypothesis concerning reviews’ themes. The findings suggest that previous theories that are valid in other sectors may be applied for the book sector as well, but there is the need for further research, especially regarding the written comments. In fact, the themes that were disclosed are new and need to be proved. Also the reviews length seems to have any clear relationship with perceived helpfulness.