I had never heard of this book before my son received it as a gift. He was about 9 months old and would insist that we read it again and again. He is now 4.5 and still likes it. And his little brother has enjoyed it just as much. The illustrations are fantastic and its fun to search for Marvin on every page. I highly recommend this book. I also love the language - it uses fantastic, descriptive words. My soon was 2 and used the words mesmorized and exhilarating because he learned them from this book.