Hide default value in form Ruby

Question

I have a form and when I set a value, the value is displayed in the field, how to not display the value but keep the existing values when submitting the form:

Here is my form :

= form_with model: resource, local: true, url: author_path(resource) do |f|
  .form-group
    = f.label :books
    = f.text_field :list_books, multiple: true
  .form-group
    = f.label :title
    = f.text_field :list_books, multiple: true
  .form-group:
    = f.submit 'Save'

For example, if in a first time I set : books to fiction and title to planet of apes

When I will go back to edit this resource, I will see in both fields fiction planet of apes because my field list_books is ["fiction", "planet of apes"]

I can't go with an empty value in my field because I want to keep the existing values on submit For example if I submit another time the form with a books : "scary" and a title : "scream" I would like to have ["fiction", "planet of apes", "scary", "scream"]