The Eleventh Hour by Graeme Base, 1989.
Horace the elephant is turning eleven years old, so he’s invited all of his animal friends to his house for a costume party. The best part will be the extraordinary feast that Horace has created himself with all kinds of cakes and pastries and other desserts. But, Horace refuses to let his friends eat any of the goodies until after they’ve played the party games. The guests have a lot of fun, but through all the games, they’re still thinking about that glorious feast. Only, when they finally go to eat, the food is all gone! Who could have taken it?
This picture book is actually a puzzle book, with puzzles difficult enough to even challenge adults. Hidden within each of the large pictures taking up the entire page of each page in the book, are secret messages that hint at the identity of the thief, who is one of the party guests. Some of the messages are in code. Although a young child might enjoy the pictures in the book and the rhymes of the story, it would take someone older to be able to solve the puzzles.
There is a way to find the thief without finding the hidden messages or solving any codes, but it still requires attention to detail. There is a section in the back of the book that explains everything, pointing out all the secrets that you can find in the pictures, including the names of one of the giraffes and the swan, whose names are not given in the story itself.
But, don’t skip straight to the answers. As Base himself says at the beginning to the section of answers, “the getting of wisdom is no match for the thrill of the chase, and those who choose the longer road shall reap their reward!”