Steven Boyett's Ariel was written about twenty-five years ago; I heard about it by reading about a sequel that is coming out about now. The world has Changed -- technology doesn't work, and magic creatures wander about. The hero, Pete, finds a young unicorn whom he names Ariel, and they become familiars: a pair linked together by love and magic. Unicorns can do magic, but they are only available to virgins. This is not an issue at first, but later Pete finds that restriction a bit chafing.
Of course, the necromancers, sword masters, killer griffins, and unicorn horn collectors distract him from his girl problems a bit. It's a fun ride as long as you remember that Pete is a young boy whose almost terminal testosterone poison renders him dumb as a stick. Most of their journey is marching to New York so they can be captured by the big bad necromancer. Luckily the trip is interesting, because the goal is idiotic, as they realize seconds after arrival. I felt echoes of Huckleberry Finn, with Jim rafting down the Mississippi towards New Orleans, because that's the worst place for him to go.
The worst part of the book is the ending, which Boyett even acknowledges in his afterward. It's not so much that the boy and the unicorn have to separate, it's how that happens, and how little control either have over it, and what Pete decides to do with the rest of his life. That stuff made me recoil a bit. I don't think betrayal is a good place to start a new relationship, that's all. I shall pretend the last few pages never happened, as I had to do with the last minutes of the latest Terminator movie. B-.