As an author, I welcome both good and critical reviews. I believe you have something to learn from the opinion of everybody who reads your books.
As a reader, I tend to be a little strict. This is why I'd like to explain my system of rating books.
1 star: I couldn't finish the book.
2 stars: I finished, but it took me considerable effort, and I had to push myself to overcome my reluctance. These are books with serious faults, which I would not recommend.
3 stars: The book has faults, but I can imagine that other people, who have different tastes than me in style, language, or content, might like it.
4 stars: A good book, with only minor faults, which engaged me and made me feel good.
5 stars: A stellar book. One which I will not forget. Content, language, style, all unique.
If I rate your book, in most cases the rating will come with a review, so you can see exactly what I liked and what my issues with your book where.
Happy writing, happy reading!