The book "The Last Unicorn" by Peter S. Beagle tells the poignant story of a unicorn who embarks on a quest to discover what has happened to her kind. As she journeys through a world that has forgotten the magic of her existence, she encounters various characters who reveal both the beauty and sorrow of life. Through her experiences, the themes of loss, longing, and the quest for identity become central to the narrative.

A notable quote from the book is, "for no one can keep a unicorn in his head for long." This reflects the idea that the pure and ethereal essence of the unicorn is fleeting, much like the dreams and hopes we might cherish in our minds. The story captures the struggle to hold onto such fleeting beauty and innocence in a world that often forgets the wonder it once knew.