Less Than a Day by April Kelley

Opposites attract in a major way when Upperworld Humans and Otherworld Faeries meet for the very first time.

The door between the Upperworld and Otherworld only opens twice a year. Samhain marks one of those days and even though Talli’s Oberon forbids him from leaving the Otherworld, Talli walks right through the door. Talli has never seen a real human before. Once he gets a glimpse and experiences a bit of what the Upperworld has to offer, he fully intends to go back to his friends and the library he loves so much. That is, until the first human he sees just so happens to be his soulmate.