Andrew Lang's famous Coloured Fairy Books series was published between 1889 and 1910. The Lilac Fairy Book is the twelfth and final volume. 

It contains a collection of 33 fairy tales, legends, romances and folktales, all drawn from traditions across Europe, Asia, Africa and Australia.

Henry Justice Ford illustrated it. Andrew Lang edited the book, but his wife’s contribution was significant. Leonora Blanche Lang translated or adapted most of the contents.

Note that some spoilers follow, so you might want to skip them to keep the surprises. 

Tolkien and the Lilac Fairy Book

J.R.R. Tolkien enjoyed all of Lang's fairy books, but like The Red Fairy Book, The Lilac Fairy Book has a documented connection with him. In March, 1939, he delivered his essay "On Fairy-Stories" as the 12th Andrew Lang lecture, at the University of St Andrews in Scotland. In this essay, he mentioned The Lilac Fairy Book.