The Night Prince by X. Aratare

Best friends Declan and Finley’s normal lives ended the day the Leviathan broke through to Earth. Only the arrival of the Sun Elves–and their powerful King Aquilan–saved humanity and drove the Leviathan back into the Under Dark.

Now Declan, Finley and the rest of the survivors find themselves in a new world full of magic and danger where elves, dwarves and other high fantasy beings are real and their neighbors. Whether the humans or the high fantasy beings want it or not!
Working at a dwarven tavern, Declan wants to keep a low profile, but when he starts exhibiting dark powers no human should have, he draws the interest of the Sun King himself.
Aquilan, the Sun King, in turn finds himself captivated by the supposedly human young man, and determines to uncover the truth behind Declan’s powers, even if that truth makes Declan his enemy.

In turn, Finley desperately wants to be the first ever human to gain magical abilities. He finds an unlikely ally in this quest in the Sun King’s rakish best friend Lord Rhalyf. But is Rhalyf’s help born out of kindness for an underdog or because he has reasons of his own to stay close to Finley?