Darkborn, book 2: Lightborn
Alison Sinclair2010

The Darkborn aristocracy has rejected magic, viewing the pursuit of science as the only worthy goal. But Lady Telmaine Hearne does not have that luxury. She has kept her own powers secret, fearful of being ruined in society...until her husband Balthasar draws her into a conspiracy to protect the archduke and his brother against a magical enemy. But who will protect them from her?