The Last Unicorn (1968)

A unicorn leaves her forest to discover what has happened to the others of her kind. Beagle gives the quest wit and a melancholy interest in love, age and the limits of wanting. The fairy-tale shape is easy to recognise, while the characters keep complicating it. Read this if you want to meet fantasy on its own enchanted ground through a complete central quest; later stories return to the world, but are additional reading.