INCENSE TO IDOLS (312 pp.)Sylvia Ashman-WarnerSimon & Schuster ($3.95).
One excellent novel is just that: two of them by the same author form strong evidence that the world has another fine writer. Sylvia Ashton-Warner's first novel. Spinster, astonished critics last year with its power, insight, and. to use a phrase of her own, pride of word. The only reservation tenable was that since the author, a middle-aged New Zealand schoolteacher, had written of a middle-aged woman who taught school, it was possible that the force of her novel sprang from circumstance, not art....