One of the best fairy tales ever written.
The White Deer is one of James Thurber's three(ish) book-length works, the other two being The 13 Clocks and The Wonderful O. The White Deer is the best of the three.
The story starts out pretty well, but by the 20th page it begins to look like it's going to be a showcase for Thurber's word play (babbling) -- Thurber is a great fan of alliteration, and it shows. But then the Princess sends the princes out on their respective quests, and things pick up -- and better yet, it turns out that there is going to be a real plot. The first prince adventures into word play and serendipity, the second into satire and chicanery, and the third (he's the one we want to win) into irony and the mandatory battle with the Black Knight. In the end no-one ends up too bad off (except the dead ones), and it's a generally happy ending all around (that's all I can say without giving away too much).
The White Deer might be classified as a children's book -- although in my local public library it's in the General Fiction section. It's suitable for children to read, but the word play and the unusual words slow down the reading in some places, and might make it a little hard for younger kids to puzzle out. It should be a great read-aloud book, tho. If you have a quick tongue.
Most likely Thurber illustrated all of his books the first time they came out, but these days his other two books have been re-illustrated by Marc Simont. The only two editions of The White Deer that I have seen are illustrated by James Thurber himself (this is a Good Thing).
And it has a good epilogue.
You just can't beat a good epilogue.