I sometimes use Goodreads reviews to help me decide whether or not to try a new book. It seems most books I look up have an overall rating of about 4 to 4.5 stars, so I don't pay too much attention to the overall number.
Sometimes in spite of a overall high rating, the reviews on the first page (when sorted in Goodreads default order) are mostly negative. Based on my past experience, this is not a good sign.
If most of the reviews on the first page are positive, I will start by reading any 3-star reviews as they are often more even-handed regarding both positive and negative aspects of the book.
If there a mix of positive and negative reviews, I will read a couple of the 1-star reviews to see why people didn't like the book. Sometimes it's personal - the reviewer hated the writer's political or religious point of view, or it's just not the reviewer's usual type of book. However, sometimes one-star reviews state that the book was badly written or poorly edited, with grammatical errors, glaring plot holes or anachronisms, and I would definitely avoid such a book.
If the reviews are overwhelmingly positive, but the reviewers seem to be barely literate, or if most of the reviews contain flashing cartoons or photos of TV or movie actors intended to represent the characters, I figure I am probably not the book's intended audience
