I bought this for big brother expecting a baby sister. I assumed the baby in the book would be genderless, just "baby". Some pages have a baby brother and others having a baby sister....very confusing for young children who are already confused.
I bought a number of books for my 2year old in preparation for our new baby, but this one has been the best. It's not dippy, drippy sentimental, and doesn't use euphemisms that sail over a 2 year old's head. Just a few simple, concret examples of what big sister can do that baby cannot in the areas of potty, dressing, eating, etc. I waited until the baby was 4 months old and for the big sister to master some of the examples in the book before breaking it out. It's been on the must read list every night and the big sister frequently just carries it around the house while engaged in other play. She is very proud to be doing the things that big sisters can do. I think this is perfect for a 2-3 year age gap and could spread a little further. We've loved our other Katz books, as well. Our big sister has memorized each big sister task and we "read" it together which is even more fun.
My son loves this. After reading about three times, he'd already memorized a lot of it (which makes him even more enthusiastic about reading it). And, he has "learned" some things about babies in the process -- will tell us about big boy underwear and how abides drink milk and can't talk etc. Our second hasn't arrived yet, but this seems like a good book for helping prepare toddlers for becoming big siblings.
This is age appropriate for up to age 3 I would say. I bought it so my son wouldn't feel left out that his sister was getting a whole bunch of books to prepare her for the baby and all though it is very cute it really isn't age appropriate for him at 4, he is very bored by it. It is well written and well illustrated as most of her books just for a younger child.