CREATE OR REPLACE PROCEDURE SYSTEM.Book_Test (@id NUMBER) AS
DECLARE
judul1 VARCHAR2;
BEGIN
SELECT judul INTO judul1 FROM BOOKS WHERE id_book=id;
END Book_Test;

Pls check your parameter (@id number).
You call wrong parameter in your query 'WHERE id_book=id'.
You don't have parameter 'id' but '@id'.

HTH,

Zettira