Piers Anthony 
Beetle Juice 

A were-unicorn searches for the meaning of life, love, and sex in this novel of shape-shifting fantasy from the New York Times–bestselling author of Amoeba. In a tiny village, just off the universe-spanning trail of the Amoeba, young, telepathic were-creatures are schooled in the mystery and wonder of the human body—its practicalities as well as its pleasures. Eager to discover their alternate selves, they marvel at the possibilities. But when precocious were Wetzel, an infinitely curious and adventurous teenage boy—and unicorn—is enlisted into sexual service, his life is endangered by his own horn, a valued commodity. Villagers would kill for it, so Wetzel has little choice but to flee and find his destiny on the trail. But his personal quest takes a backseat when he joins human Tod Timmins and his bizarre band of outcasts on a calling of their own. And though they don’t know it yet, Wetzel’s sexual prowess is imperative to the success of their mission. Navigating the trail, this motley crew will discover new worlds as well as friends and foes of various species as they journey ever closer to restoring the balance of their existence and the universal justice the great Amoeba desires