You can start using the notebook as is, but by adding a zipper case or a pen holder, you can increase its storage capacity. If you add a connecting band, then you can even increase the number of notebook refills that go inside the notebook.
This consists of a simple cow leather cover made in Chiang Mai, Thailand and a refined notebook with Designphil’s original paper used that is made in Japan.
Issues to be aware when buying and how to maintain the leather
How to Set Several Refills to TRAVELER’S notebook with a Connecting Rubber Band