What's the value?
Besides fun, it's about reading, following directions, figuring out how to do the activities, thinking, breaking out of "the mold," imagining, interpreting, and experimenting.
The nice thing is, there is no wrong way to do any of it.
You can use it as a reward or just go crazy with it all day long. Or do one or two activities each day. It's really up to you.
This can also be really fun project to do together. Parents and kids will get a lot of joy from discovering how each other might approach any one page.
Despite the fun, it's a really good way to develop thinking skills while "thumbing your nose" at convention.