1. Always read the whole of the book before you write your review.
2. Don’t undertake to review a book
if it is written in a genre you particularly dislike.
3. Review the book the author has written,
not the one you think he/she should have written.
4. If you have prejudices…
face them frankly and, if appropriate, acknowledge them.
5. Be scathingly witty if you must and can,
but never be deliberately cruel […]
6. If you absolutely hate the book
and have nothing either interesting or positive to say, why review it?
7. If you are given a book to review by a close friend
and you strongly dislike it, don’t review it.
We none of us like hurting our friends
and the temptation to be over-kind is too strong.
8. Resist the temptation to use a review to pay back old scores
or to vent your dislike of the author’s sex, class, politics,
religion or lifestyle. Try to believe that it is possible
for people of whom you disapprove to write a good book.
What would you add to this list?
I appreciate personal interactions with the book.
I like to get to know reviewers, especially bloggers.
A Living Pencil 
I dont really have anything to add to PD James’ list other than commentary One of the first things I do when checking out a book at Amazon is to read a negative review. So, I think there is a place for that, even tho’ I prefer to write positive ones.Because I believe that no one is totally objective, I tend to search out connections, i.e. publishing house, alma maters, endorsements, as indicators; not necessarily agendas, but perhaps tell tale signs of something.
She really puts it so well! I would maybe add that you shouldn’t expect this book to be like the last book the author wrote. So many times I read negative reviews that say, “I loved such-and-such-a-book by this author and loved it and so wanted to read something just like it and was disappointed” or something akin to that. While some authors write each book in a similar style, others write in a variety of styles and each book should be judged on its own merits, in my own opinion.I only review books I finish, and rarely finish books that I’m not enjoying, so it’s rare to find a negative review on my blog. While some people may think that means I’m “too nice” or not critical enough, it doesn’t bother me.Carrie