I normally really like Karen Katz books but this one is just ok, I wouldn't recommend it.

Our little girl, currently in the potty training process, loves this book!

We got this book for my 19month old who is beginning the potty training process. She loves it and has me read it over and over, saying, "Uh-oh! Pee-pees!" when we read about 'accidents', as well as patting her head - then mine - each time we get to the part where the girl's little sister likes to put the undies on her head. I'll be using the book to introduce my daughter's big girl undies and potty training process to parallel the little girl's process in the book.
If your child is also familiar with Karen Katz' work, she/he may also try to lift the flaps that aren't there, but my daughter got over not having any flaps to flip after the first few reads.

My daughter (~28mos) loves this book, along with the other Karen Katz books. I dont know what it is about these books but she always goes back to these.

daughter loves it! and I love how the undies are actual cloth :)