As someone that does review a lot and I am sure I am one of the people being discussed. I personally am surprised as many people seem to like my reviews as they do, yet I keep getting people not just publishers asking me to review stuff*shrug*. I personally prefer to give a bullet point review of here's what you get and let people make up their own minds. The rating system is flat flawed IMHO. The reason i say that is it really comes down to a matter of taste on what the reviewers likes and dislikes are. I try to minimize that with my reviews but it is still true. I think reviews would be better and more helpful with out a rating system personally.
I do the bullet point review because that's what I want to know. I care more about what all is in a product, less about what the reviewer thought of it. Plus I fully admit I don't care a ton about the rules. To me if something plays well/works and is interesting, then I am happy even if it breaks a rule to do it. End on the other hand tends to care more about the rules. I also don't like to give spoilers while End doesn't mind.
As for the lack of low reviews, that's true and I dislike doing low reviews. Not for the reasons some might think though, plus what each of us consider a rating varies. For one I normally have trouble finishing reading something I would give a low review to and two the main reason i do reviews is to inform people and help the hobby, by pointing people towards the stuff I think is good. Which helps sales (hopefully) which increases the odds of more products being made.
For those curious how I view the rating system.
5 star = Product with lots of useful and interesting idea's for a reasonable price.
4 star = Product like a 5 star but needs a little more polish or it has some good and interesting stuff and some filler and/or stuff that needs work.
3 star = solid product with some cool bits but either needs a lot of polish/work or works as intended but nothing special. and/or a 4 star priced way to high.
2 star = Needs to much work to be usable, which often means I never finish reading it. and/or a 3 star that is priced way to high which is usually the only ones this low I finish reading.
1 star = waste of my time to read it, which means I never finished reading it.
As for using reviews what I would do and I think is best since reviewing is very subjective. Is look at the stuff you own, go check the reviews. If you can find a reviewer that seems to give a similar rating to a book as you would give on a lot of stuff then you found someone that has similar style and taste and just pay attention to them.
But then if you are lamenting about a lack of good reviews, maybe you should start doing your own reviews and doing them the way you think they should be done.
