library/library_member/views/book_list_template.xml

<?xml version="1.0" encoding="UTF-8" ?>
<odoo>
    <template id="book_list_extended"
              name="Extended Book List"
              inherit_id="library_app.book_list_template"
    >
        <xpath expr="//span[@t-field='book.publisher_id']" position="after">
            <t t-if="not book.is_available">
                <b>(Not Available)</b>
            </t>
        </xpath>
    </template>
</odoo>