The 13th Clue by Ann Jonas, 1988.

This picture book is almost entirely pictures. The pictures present clues to a treasure hunt and reveal the true story of the book.

The book begins with a diary entry. At first, we don’t know who is writing it, but this person writes about what a bad day it’s been. We know that the person must be a kid because they mention school, and I guessed that it was the person’s birthday because people sang to them at school. But, she thinks that others have forgotten her birthday. The diary entry breaks off when the person notices a light going on in the house when, supposedly, no one else is home.

From this point on, until the very end of the book, the text is presented in the form of clues for our birthday kid (who turns out to be a girl, as shown in shadows and a reflection in water in later illustrations) to follow that lead to the place where her friends are waiting to give her a surprise party. Readers can figure out the clues along with the girl, some of which are easier and more direct than others.

I love puzzle books, and I thought that it was interesting how we don’t even know who the main character of the book is, only finding that out as the book continues. I liked the challenge of figuring out the clues as the book went along, although none of them were particularly difficult. They aren’t written in any kind of code, just kind of hidden in plain sight, most of them using objects that are part of the rest of the scene. Some of the letters of words are jumbled and have to be unscrambled. I’m sure it would seem harder to children.

This is a pretty easy book, but not one that would be suitable to read to children who can’t read themselves. There are no solutions provided to the puzzles, but that’s okay because, first of all, they aren’t very hard, and second, there are no opportunities for the reader to make choices based on the puzzles, so there is nothing for the reader to get wrong. The end of the story is obvious. Most of the fun is just studying the pictures to see the cute ways her friends decided to hide their “secret” messages. The hardest message to spot is the one written in the hillside.

The book is available to borrow for free online through Internet Archive.