The Law of Stars and Sultans by S. Young

Previously released in 2013 under the title Darkness, Kindled (A Fire Spirits Novel)

The Law of Stars and Sultans is the action-packed final installment in the epic romantic fantasy series Seven Kings of Jinn.

Ari Johnson wishes adjusting to living with her boyfriend was her only source of excitement and anxiety.
She wishes a lot of things.
But then wishing got her here in the first place.
Ari chose to be a guild hunter. She wanted to hunt dangerous jinn and destroy them before they could harm innocent people. But now that Ari is a member of the Guild, she finds herself in the impossible position of hunting her ex-best friend—human-turned-dangerous sorcerer, Charlie Creagh. As Ari struggles to come to terms with her duty, an ancient jinn and his companion want revenge on her for using the command of the seal against them; the White King refuses to give up on his quest to resurrect Lilif, and Asmodeus isn’t done toying with her.
When Ari can take no more, rushing to the Sultan Azazil’s side to demand of him the favor he owes, the events she sets in motion not only alter everyone’s lives, it kindles a darkness that shakes the realms to their very core.