The Notes Book is a consumable item used to summon the Explorer NPC. It is made by combining the Secret Note and Torn Notes #4-9 at the Jeweler. Its primary purpose is to summon the Explorer NPC.

If used during a Solar Eclipse, a portal will be spawned close to where the book was used; it can spawn on the surface, even in the air. After interacting with it, the Explorer NPC will be available to move in.