I have 'read' books with my son books from when he was a couple of months old, but none light up his face and make him shriek with excitement as this one does. He is now 8 months and it has now become a bit of a party trick to show his reaction to visitors as we get the book out, and read through the pages with him. As he is now going through a very touchy-feely stage, he also loves all the different materials,especially the very fluffy ones. I think the combination of repetition and the bold, bright colours and pictures are the key to its success. I have now also bought the That's not my train one, which is also very nice, but 'That's not my teddy' is still number one, judging by my baby's reactions to it. It is really well worth buying, even for very young babies. It is one of the very few books that really appeal to them at a young age.