My son has had this book as his favorite for more than half of his life. He's two now. He already has some 50 books, and this is his favorite, and mine too! While reading this book to him, he laughs and repeats "No, David" when David does things he's not supposed to. Afterwards, I only need to remind him of what is No, David and he understands. Interestingly, it seems as if some other (adult?) reviewers here understand the message less than he does. Regardless, it is one of the best books we own and I would recommend it to any intelligent child and parent.