If you were a child in the 70s, you may already know this book. If you don't know this particular book, you'll at least appreciate the artwork as being evocative of children's books of that time.
I was a child in the 70s. I don't remember this book from my childhood, but a friend of mine clued me into it a few years ago (thanks, Tina!), and the first time I laid eyes on it I felt like a kid again.
This book has everything a great story should have: a king, a queen, a lovely princess, handsome princes, dragons, witches, a castle, a forest, and fantastical creatures. The king is a happy king, but he has a problem. His daughter is so lovely and kind that all the princes in the neighborhood hang around the castle all day. With all those princes hanging around all day, the king feels obligated to share his beloved Pickle-Chiffon Pie with them. The king is tired of sharing his pie. He wants it all to himself, so clearly the princess must be married to put an end to the constant hungry visitors. The king picks the three nicest princes and sends them off into the forest to find the most unusual, the most marvelous, the MOST WONDERFUL THING. The prince who brings back the MOST WONDERFUL THING may marry the princess.
The three princes set off, and each finds quite a number of unusual and wonderful things, but one prince finds that it's really difficult to bring back the MOST WONDERFUL THING. Should he force this wonderful thing to leave its home? Or should he give up and let another prince win the princess's hand?