The 6"x5" board book edition of this book (called I SPY LITTLE BOOK) is a beautiful book to read aloud to babies and toddlers. The 8"x8" paperback version (called I SPY A FUNNY FROG) is great for helping pre-K, kindergarten and first grade children read. In May 2013 I took this photo in a kindergarten classroom. The girl held up the book and read it to the class like a teacher. She had no trouble reading "chick" because the the picture was a clue. The kids on the floor could see the text so they helped her sound out "truck." The actual teacher asked the class if anyone could find "little" on the Word Wall. This boy had no trouble doing it because it's one of the sight words that the children had learned during the year.
I SPY A FUNNY FROG and the other 8"x8" paperback books like it are not a reading program. They are supplementary. The kids are helped to read by various clues: the pictures, the pattern of the text ("I spy" starts every page), the rhythm, the rhyme, and beginning phonics skills that they are learning. Also, memorization. The next day kids in the class may pick up this book and read it easily, having experienced it in the classroom the day before. Teachers
often put two kids together to read these books so they can help each other while they play the game.