It's very cool that we can use half stars here at booklikes. It enables one to be a lot more specific about the books review. Here's how I use the stars.
5 stars-Loved every minute of it. This could be anything from great literature to a cozy mystery. If I loved it, it gets 5 stars no matter what the genre.
4 stars-This was really great
3 stars-Not a waste of time. I liked it but I've read better
2 stars-Not worth the time it took to read it. Cannot recommend to other readers.
1 star-Absolutely a waste of time and not only would I not recommend it, but I would warn other readers about what I found. (I hope that doesn't sound harsh but life is too short to read bad books)
Half stars just enable me to shade my feelings a bit.
Poor editing definitely effects my ratings. The least an author should be able to do is spell, punctuate and remember the name of their characters, in my humble opinion.