I bought Twinkle Twinkle and This Little Baby when my daughter was just a few weeks old mainly because I felt I should be introducing books as soon as possible - I did feel a bit silly in the early days going thru them. Her first achievement was to just keep shutting them, however now 15 months old I find it amazing how she reacts, they are old favorites now, her comforting reads that she instantly recognises and goes back to. She knows exactly what is coming next and gets all excited when the 'Baby is gone, Where's the Baby'. I can measure her progress against them and they are still in great condition, hopefully to give pleasure for a few more months yet.