You could earn more per hour as a migrant grape-picker than you can by reviewing for many newspapers, and the odds are that an editor will ask you to write about a bad book and that the author will hate you afterward. So why volunteer for the work?
One of the best answers I’ve heard came from the novelist and critic Rebecca West in a Paris Review interview, collected in Writers at Work: Sixth Series (Viking, 1984) and in Women Writers at Work: The Paris Review Interviews (Modern Library, 1998). Marina Warner asked West if she enjoyed reviewing for the Sunday Telegraph, then as now a leading national newspaper in Britain. West replied:
“Yes, I do. I do. I would feel awfully cut off if I didn’t review; I think it’s such a good discipline. It makes you really open your mind to a book. Probably you wouldn’t, if you just read it.”
Many critics like the serendipity or reviewing, or getting assigned books they wouldn’t otherwise have picked up, and I do, too. But I also like having to focus on books in a way that I don’t usually do when I’m reading for pleasure. You have to look harder at books when you’re reviewing them – you can never skim, ever — and when you do, you see more.