I’m a big fan of Lloyd Alexander’s books, particularly “The Book of Three”, and “The Castle of Llyr” in the Prydain Series of books. I’ve recently discovered that there are additional stories in the series that were released in a book entitled “The Foundling, and other tales of Prydain”. The book is very short, only 94 pages, and I read the book in its entirety in the day that I received the book, but all of the Prydain series are relatively short in comparison so is not to be unexpected, plus the stories contained theirin are fantastic so should be considered a must read in my opinion, regardless of their shortness in nature.
Here is a picture of the paperback cover. Although it is very short, I consider it a must read.