when is a 3 out of 5 star rating considered negative?

I recently wrote a review for a book and gave 3 stars for it (rating system on the site is 3 for good, 4 for very good, 5 for loved it with no 1/2 stars). I stated I liked the characters and story line but felt it was a little slow for me. I got a message from the author thanking me for the review but was disappointed it didn't rate at least a 4. I feel comfortable staying with a 3 because the book was good and the slowness I found may not be there for others because everyone perceives things differently.

 

Has anyone else dealt with this? The author didn't come out and ask for a 4 but listed an award the book won and the number of 4+ star reviews it has received on another site. I'm quite glad he defended his book because he should be proud of what he accomplished and the number of people who do like it. My thought, though, is that reviews are subjective, and are usually taken as such. And a rated book with a review to explain the review is just more information for a reader to get the right book into a reader's hands.

 

Am I reading too much from the email I received from the author? Is a 3 out of 5 review where 3 is good and recommended too tough?