A Year and a Day — Elizabeth Silver

Reserved, bookish Ben isn't looking for a relationship. Then he meets Niall, a gorgeous stranger with a knack for avoiding direct questions, and tumbles headfirst into love. Niall is perfect in just about every way, right up until he leaves town for a short trip...and vanishes off the face of the earth.

A magical being trapped in his own realm, Niall has to fight to come back to this world for the chance to be with Ben. But by the time he gets back, more than a year has passed, and Ben refuses to believe Niall's story of Fae and magic.

With only a month to woo Ben back and earn a chance at staying here permanently, Niall is willing to try anything to be with the man he loves. Then Niall's world spills over into ours and puts Ben's life in danger, forcing them work together to save Ben before their stolen time comes to an end.