These notebooks have a lot of great detail!
First, the front & back covers (top) are full color. The front has a Green Hill scene with running Eggman art (going down a hill) and a scattering of little animals & badnik robots including Ball Hog (top left) who is rarely seen. The back has hand on hip waving Sonic in a smaller scene. The two cover interiors are also full of art. One has a green hill & cave scene (with random enemies who don't appear there) while the other has art for Sonic and some badnik robots, giving the name for each item in Japanese. The inside has all nice lined paper, with logos at the top. Each left page has 'looking out' Sonic, while each right page has Eggman standing in the bottom corner.
This is a quality piece. All the art and attention to detail making every page fun...makes it a desireable collectible. It's early too, as you can tell from the Segasonic branding and Sonic 1 only content.
The other notebook (right) is thought to be released at the same time, & has a similar theme but with Egg o Matic Eggman, different badnicks interior page & various Sonic stock arts along the bottom of the lined paper pages.