Bob Moyer loves good mystery novels, and he loves New Orleans, so it’s no surprise that he is reviewing the latest Sister Holiday mystery, No. 3 in the series. Reviewed by Robert P. Moyer DIVINE RUIN. A Sister Holiday Mystery. By Margot Douaihy. Gillian Flynn Books. 336 pages. $28, hardcover. A gold-toothed, tattooed ex-punk rocker…