My 4 year old son has loved this book since he was 2. The poetry is zany ("there's a lizard in a blizard and it's fun to be outside, but bedtime's creeping closer, who will you ask for a ride?"), the illustrations are interesting and detailed. There are lots of flaps to lift, tabs to pull and twist and such interactive devices are always a hit with children.
I would sound a couple of notes of caution though. The pulling tabs aren't especially strong and a few on our book broke within a couple of months, despite my son being as careful as possible with them.
Also, this book is aimed at bedtime which we try to make a quiet and settling time. The last pages of this book contain a crunchy crocodile looking for toes to bite, a bear looking for a grrrrreat big squeeze and the "ticklemetoo" monkey. All these elements beg hysteria-inducing rough and tumble rather than sleepy settling. I challenge any parent to find a calming way to read the bit about the "ticklemetoo" monkey!
Overall a lovely book, but a touch too fragile and boisterous for bedtime.