Down Comes the Night by Allison Saft

Wren Southerland’s reckless use of magic has cost her everything: she’s been dismissed from the Queen’s Guard and separated from her best friend—the girl she loves. So when a letter arrives from a reclusive lord, asking Wren to come to his estate, Colwick Hall, to cure his servant from a mysterious illness, she seizes her chance to redeem herself.

The mansion is crumbling, icy winds haunt the caved-in halls, and her eccentric host forbids her from leaving her room after dark. Worse, Wren’s patient isn’t a servant at all but Hal Cavendish, the infamous Reaper of Vesria and her kingdom’s sworn enemy. Hal also came to Colwick Hall for redemption, but the secrets in the estate may lead to both of their deaths… Read more.