The how you rate question is interesting, there does appear to be a section of people that give 5 star ratings very freely, whereas to me giving a book 3 stars doesn't mean it wasn't very good but that it was ok. My 5 star books have to be very, very good. I may be wrong but don't the star ratings when leaving a review on Amazon suggest 3 - OK, 4 - enjoyed it, 5 - loved it, or something like that?
The average review rating means little to me anyway, I tend to look at how many there are of each rating, so if there are 20 5* reviews and 2 or 3 of all the rest it's good, but if there are 15 5* reviews and another 10 1* or 2* then I'll give it a miss. And when reading the reviews, I tend to ignore the 5* & 1* reviews. So DrNefario, your reviews are pretty wasted on me :-)
That's why its just a rough guide, everyone writes and reads the reviews in their own way. Don't they?