Looks like the perfect book for my toddlers that love light switches. One question I don't see answered is what type of battery is it? We are trying to avoid coin batteries with their curious mouths.
It uses a small CR2320 battery. To access the battery you'll need to remove a sticker on the back cover, and then the battery is glued in with hot glue, so you'll need some pliers to remove the glue, and then you'll need a small tool to push the battery out of the circuit board. Rest assured, it's not going to be an easy battery to remove.