Peter S. Beagle published The Last Unicorn in 1968 and it has ever since been one of the most popular and widely read fantasy novels in the world. Beagle afterward would say that while the idea for it came to him very suddenly, actually writing it was immensely difficult; it took two years to work out to his satisfaction -- non-consecutive years, since he gave up on the project for a couple of years in the middle -- and the final result was very different in setting than the one he had first attempted. It has been more than a few years since I last read it, so it seems a good fortnightly book to use after some of the relatively heavy works I've done recently.
The book was adapted into an animated film version in 1982; it was a commercial flop at the time, but there have always been those who have liked its rougher, less packaged approach to animated storytelling. I am one, so reading the book gives me a reason to re-watch that as well.
