Yes, if you have explained the details privately to the author and they tell you go ahead and post it, go for it. There is nothing wrong with constructively critical reviews, and authors should welcome them as long as they are addressing the book. They provide ways for the author to improve the next time!

No expert, I, but I have an understanding that some readers are suspicious of all five-stars for reviews. They think that will reflect reviews from friends and family rather than the average reader. I know that I myself read the three-star reviews first. Also, I think, at the beginning of a writer’s career, it is important to have a great volume of reviews even if some of them are negative.

Sadly, witty critics (who can be very insightful) are few and far between and people confuse them with catty critics. Being bitchy to show how “clever” you are is never good and reflects worse on the bitcher than the bitchee.

Critical book reviews, if written respectfully, are gold to an author. It provides them with a way to improve next time around. But RESPECT is the key. Too many people nowadays think it’s fun to write reviews attacking the author and try to destroy their careers. The trick is to walk a line where you provide, as you say, constructive criticism in a respectful manner. I saw an awesome blog piece the other day that beautifully explained the difference; reblogged it over at my place, Now is Gone. I’ve blanked out on the blog name where it was originally, but it should still be on my front page, just down a few, and you can follow the link back to the original.

It’s part of your brand. Do at your own risk. You have a right to do a lot of stuff. My job is to point out areas where you need to be careful.