A book review is a conversation that excludes the author of the book. It addresses the potential reader. A reviewer isn't paid to be right, just to make a case for or against, and to give pleasure either way. I didn't enjoy Margaret Atwood's The Blind Assassin, which I thought structurally defective and basically novelettish. Its winning the Booker in 2000 didn't prove me wrong, any more than it would have proved me right if I had liked it.
Both my parents were lawyers, and you could hold that accident responsible for something forensic about my approach. I don't set out to put a book in the dock, but perhaps I do put it in the witness box and rake through its testimony. In the review of Michael Cunningham's By Nightfall which brought the Golden Hatchet my way I grilled the book fairly intensively, but I tried to play by the rules. It always seems a good idea to quote freely from a book, to back up points with solid evidence. The only "bad" review in my book is one whose writing is soggy, its formulas of praise or blame off the same stale shelf. A reviewer and a critic play different roles, though the same person can take them on at different times. A critic has some sort of authority, a claim to long experience or deep immersion, a marination in a certain class of literary product. A reviewer has no necessary knowledge, even of other books by the same author – there's no shame in flying blind. If a book isn't rewarding to read in isolation, then there's no point in invoking any larger perspective. Forget the hinterland! It's a mistake to imply that readers are being inducted into a mystery. They're being guided to pleasure or warned against disappointment.
His full piece at The Guardian.