The idea is splendid and I love how it's executed. I assume it can be used mainly for some book ads and promotions but this can be a great inspiration for a home library or child's books.
No much effort is needed to print or even draw a custom made jackets and make a matching bookmark. Not to mention how fun, creative and thought provoking it can be. It's a great way (and nonconventional, read less boring!) to engage children into discussion about literature, books, the plot, book characters an so on... and at the same time improves their cognitive and manual skills. I'll definitely give it a try :)