The cover material used for these 'Amazing' notebooks is quite interesting stuff. It's made by Texon, and while it looks and feels like a thick card, the cellulose fibres are impregnated with latex. The result may look like card, but it's waterproof, and surprisingly strong and wear resistant.
You may know a very similar material, as Texon also make the stuff used for jeans labels. And the label on your Levi's looks like card, but it stands up to being worn and washed as many times as the denim itself does. So when you use it to make the cover for some (already pretty impressive) notebooks, the result is quite Amazing.