Summer Bound by Melissa Marr

After centuries of frolicking as a Summer Girl, Siobhan isn’t sure she’s ready for her new life. Promoted to Summer Court advisor alongside Tavish, Siobhan suddenly has responsibilities and a chance at romance–until she and Tavish are at odds as they help guide their queen through a life-changing revelation.

Aislinn, former mortal and current Summer Queen, thought she’d already faced the most difficult obstacles fate could throw her way. Losing her humanity, becoming a queen, loving someone who spends fifty percent of his time in another world, facing the embodiment of war in a battle, Aislinn is ready to make sense of her new “normal.”

No one is prepared when the former Dark King, Irial, arrives with a secret that could challenge the delicate balance between the Faery Courts.