I found this usability study very interesting and very relevant to writers.
According to the study:
The flipside of this is important to be mindful of: users won’t necessarily consider the product with the highest rating average the best-rated one. Indeed, during our 1:1 usability tests, the subjects often show greater disposition towards some products with 4.5-star averages than some with perfect 5-star ratings due to the number of votes these averages are based on.
For instance, most subjects would pick a sleeping bag with a 4.5-star rating average based on 50 reviews over other sleeping bags with perfect 5-star ratings that were only based on a few reviews – they simply didn’t find the latter to be trustworthy.
So, authors — don’t worry so much if you don’t receive all 5-start ratings. Focus your energy instead of getting as many reviews as you can, because the number of reviews matters as much as the aggregate rating itself, if not more so.
How to get reviews? Simply ask anyone who tells you they loved your book to “go public” with their admiration, whether on Amazon, Goodreads, B&N, etc. Most non-writers don’t realize how helpful it is to have good reviews on online retail sites, and most are happy to help!