The boys got sticker books in their stockings this year, and don't you think sticker books are the perfect format in which to enjoy a sticker? Because consider: it's so fun to have a sticker, and to peel it off its backing, but then what? There's so much uncertainty in that sticker's fate: will it become fuzz-covered from being stuck and re-stuck on one's shirt? will it meet its demise in the washing machine? will it be stuck secretly on furniture, never to be removed again? will it be stuck on a scrap of paper and then lost? will it be stuck on a paper and then unceremoniously ripped back off because the paper it was on was, in fact, a utilities bill or other necessary document?
With a sticker book, you have a place to put the sticker (usually an exact outline into which the sticker fits perfectly, which is so satisfying in and of itself), and it's accessible, so you can enjoy it immediately, but also archiveable, so you can keep it and look at it later. And you get the fun of peeling the sticker off, and sticking it down, without the worry of what will happen next. Perfect.