Her Tyrant Alpha by Emily S Hurricane
She was born in fire. He was forged in ice. The clash will scorch them both.
After a disease wipes out all human life on earth, the world is left to the werewolves. As packs organize and claim territory, an opportunity arises to collect information from a Viking pack headed by the dangerous alpha, Nolan Frosaker.
Ashelin jumps at the chance to go undercover, but only partly because she wants to contribute to the mission. The Viking King intrigues her, and she has unique talents that will get her close to him. What she doesn't anticipate is Nolan's own unique talents, and how quickly she desires to be completely at his mercy.
*This story takes place in the Bloodlines universe, but can be read as a standalone. If you're curious about the apocalypse and want more of Ashelin and her previous pack, there are multiple seasons live of Bloodlines as a companion to this book!*