I ask this question because I should have thought that part of the purpose is to tell potential readers whether the book is actually any good or not.
Well, I read a double-page article about a nonfiction book recently, and it did three things wrong in my humble opinion.
Firstly, it included so much detail about the book that unless you have a really deep interest in the central idea as it relates to writing you probably won't need to buy the book.
Secondly, as far as I can tell there was no questioning, no critical comment or insight. It is all very descriptive, or at least too descriptive for my liking. I prefer a more analytical approach.
Finally, I don't think the author said whether he actually liked the book or thought it was value for money.
So, all things considered, I don’t think that so-called review was worth the time I spent reading it.
This is an updated version of an article that first appeared in my Write! newsletter: