This was one of my favorite books growing up. I spent hours finding the clues on each page and trying to solve the mystery of who stole the feast at Horace the Elephant's eleventh birthday party. The book is clever, fun, engaging, and the illustrations are beautiful.
There's also a clock on each page, so you can have your child or students practice telling the time on each clock for a review if they've already learned this. Honestly, it's a very small part of the story, so it's not a lot of practice, but the book is so much fun and you can also work on other skills, such as reading, writing, and problem-solving.
When I was reading the book with a group of elementary school students (and I also with my son), I made a set of "detective notes" for children to make notes about the clues on each page and also record the time on each page. You can download the detective notes here: http://www.positivelyautism.com/downloads/DetectiveNotes.pdf