library/library_member/views/book_list_template.xml

<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>