Jonathan Mayhew recently put in a much more elegant and succinct way an idea I have tried to convey in some previous posts of my own about book reviewing:
My strategy for reviewing is to perceive the book in as precise a way as possible rather than to praise or dispraise. The praise or dispraise, such as it is, should arise organically out of the perception.
This is an admirably concise way of indicating why mere "praise or dispraise" cannot be the most important point of book reviewing/literary criticism. Such value judgments cannot be trusted at all if they're not supported by a clear "perception" of what the work under review actually does, what, to the extent it can be gleaned from the text itself, the aesthetic intention of the work seems to be. Thus a credible piece of criticism must include some degree of informed description of the work at hand. Jonathan is speaking specifically of poetry, but I believe the same principle he enunciates applies to fiction as well.