1) Since Janelle is a visual learner she befits from pictures. Each picture is labeled as to what it is so you are learning about all kinds of things, not just putting the sticker wherever you want to.
2) She has to use her hands to peel the stickers from the sticker page being careful not to tear them, and then place them in the correct place. This is a great exercise in dexterity and hand eye coordination which she will need for writing among many other things.
3) She can't do this by herself. Each sticker is numbered and has a certain place. So she needs me to read the numbers for her and show her which page and place to put them. Which lends itself to a bonding experiences and increases her chances of academic success.(See below)
4) It makes her happy. She loves stickers and has since yesterday begged me to do sticker book with her several times.
Not bad for $1.
Read here for more info on the benefits of bonding.