A bad review hurts. Not a critical review but a bad review - the smug smart-arsed review that lets the reader know that reviewer is a very clever person, far cleverer than any published author, or any publisher, editor or anybody else involved in the publishing process.
Reviewers generally do a really excellent job and are an important, valued part of the publishing community and fair criticism that includes that good and the bad is good for us and for our authors. We get better no feedback from authors than by sending them a good review.
There are some reviewing habits that get right up my nose though, and they often appear as a cluster. The worst of these sorts of reviewers will writer reviews with all the following sorts of characteristics. (I'll call this hypothetical reviewer by the usefully androgynous name of "Sam" so I can avoid that "he or she" thing.)
1 Sam retells the plot of the book,
2 Sam applies an adult sensibility to the assessment of a children's book, without considering how the reader of an appropriate age would respond to the text.
3 Sam judges all books by the criteria of literary fiction.
4 Sam presumes to know what happened in the publishing process. Something like: "The publisher just printed the author's first draft and didn't bother with any editing."
5 Sam then blames the publisher for a lack of editing rather than honestly critiquing the book.
6 Sam criticizes the book for failing to meet the criteria of some old saw like "show don't tell". I often think that this is what Sam has been taught in a creative writing class and as a clever student Sam has been too quick to ingest it. (Don't write books according to such advice - do what the work itself needs, is my advice)
7 Sam criticizes the punctuation and grammar. This carping demonstrates Sam's superiority to the author and editor. (I'm thinking that Sam is the disciple of an ancient edition of some school textbook.)
8 After reading the review I'm left with the impression that Sam believes that anything done "over there" is far superior to anything done here - with the exception of Sam's own work.
Like Powerpoint Bingo, it would be worth seeing how many of each of these sins appears in each review you read. All eight is a major achievement by the reviewer.