The practice of reviewing a book without having read it inevitably brings Oscar Wilde into the discussion: Wilde (the patron saint of non-readers) recommended six minutes as the proper time to spend reading a book for review, and advocated reviewing as a good way of talking about oneself.
Books we have never read - TLS Highlights - Times Online, via Laura/Frothy Paradise (Years ago, a friend of mine once told me I’d be a good book reviewer. I was slightly flattered at the time; now I wonder if said friend was familiar with Wilde’s view—probably—and as a result feel rather put off by the implications!)