The “Left Behind” novel series has given Christian fiction new respectability. Last year’s installment, “Desecration,” dethroned John Grisham from a seven-year reign at the top of best-seller lists. The 10th and latest volume, “The Remnant,” logged 2.4 million orders in the two months prior to its July 2 release.     But the novels have also renewed discussion of end-times theology.…