I love this book. The pictures are beautiful and have an almost luminous quality, and the idea of lying in bed, looking at the clouds in the sky and imagining all sorts of images, appeals to me. My daughter (2yrs 9 months) is, however, not very interested. The book is all about opposites, and therefore, on one level, is relevant to a 2 year old, but I think you need more of an ability to think about abstract ideas than a 2 year old has, before you can really enjoy this book.
My daughter is 2 1/2 and adores this book. She can recite the opposites all by herself and loves pointing out the details in the pictures too. I like that the book doesn't use the more obvious opposites that appear in so many kids' books. I think the illustrations are lovely, and particularly like the way on many of the pages the illustration follows on to the next page. A good bedtime story.