The Dublin Murder Series are a good example of the shortcomings of the GR rating system: 
 I gave 4 stars each for the first three books, while my appreciation of them differed a lot: 
 1. In the Woods 4,25/5 
 2. The Likeness 4,5/5 (once you get past the doubtful coincidences and the Secret History-resemblance 
 3. Faithful Place 3,75/5 
 See what I mean? 
 Btw. these were my very first audiobooks and I love it!