Loved by all my grandchildren in turn; read again and again, such a simple book, don't know why they find it so fascinating - from a one-year-old all through the years and still wanted at age seven. Kept renewing it at the library and eventually just had to buy it for the latest child.
My son who is nearly 3 adores this book. It is a great way of getting them to understand opposites and he finds the page where they are too big to get into the small tunnel hilarious. Hugely recommended.