It can only belong with the individual method if the request creating the textbook already has an ID in mind for that textbook: if that's the case, then POSTing to the URL that corresponds to that ID will create the textbook if it doesn't already exist, and update it if it does. If the client doesn't have an ID in mind for the textbook yet, but wants the server to assign an ID, then it needs to use the collection method; it can't address the individual method without an ID.