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 a very specific (read: ‘niche’) aspect of educational Computing 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. To be frank, it read more like an advertorial than a book review, and I was left wondering how much the newspaper had been paid by the publishers for writing it.

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.

When I review books I do so in a critical manner — using that word in the intellectual rather than the negative sense. I realise that that that may upset some authors, since so many authors think they ought to be the recipient of the Nobel prize for literature (see A Writer’s Life Part #1: O vanity, vanity). Well, not to beat about the bush, tough. My duty is to readers and potential readers, not the author.

For more opinionated opinions about education, but not necessarily edtech etc, please see What now?