I like to think of this as a grading system: 1 (F), 2 (D), 3 (C), 4 (B), and 5 (A). So, then most books then should be at least a C (AKA 3-Stars). A 4-Stars then is actually quite good, but not perfect. Most of my reviews will most likely be 4-Stars.
At first I thought about being more lenient, but it concerns me how easy it is to get a 5-Star rating on places like Amazon. When I get the books I am horrified at the quality of the novel. So, read the reviews first then consider the rating.
After some reviewing I have come up with a format of reviewing:
Intro: Basic information like what number of the series this is.
Basic Plot: Think of this of the synopsis found on the back of the book.
Background: General information about the book itself or my experience with it.
Female Lead: The characterization of the heroine, including a memorable quote.
Male Lead: The characterization of the hero, including a memorable quote.
Theme Summary: This seems to be the fulcrum of a rating of 3-Stars or 4-Stars. If I can not come up with a decent theme then I make it a 3-Stars.
Strong Points: These are the important strengths of the book.
What could be better: If this is not a 5-Star book, then there could be things done better.
Conclusions: This is my bottom line of the book, including if I would recommend it.