Best Beast by E.J. Russell

Being invisible makes it really hard to get laid.

When half-human Kai Schiffer steps into the Interstices—the post-creation gaps between realms—his supernatural half kicks in and he literally disappears unless…well, don’t ask.

But in a stroke (heh) of good fortune, Kai finally has a chance to show his face (and other parts, stars willing) to his long-time crush Jovan Kos—Interstitial Law Enforcement agent, wolf warrior, occasional berserker, and best man at their mutual best friends’ Imbolc wedding.

Jovan, who’s half in love with Kai already, is grateful his best man duties are light enough that he can focus all his attention on Kai. After all, with Enchanted Occasions Event Planning handling the Olesson-Pakulski wedding, what could possibly go wrong?