<form class="field is-grouped is-small pl-2" action="/edit-readthrough" method="POST">
    {% csrf_token %}
    <input type="hidden" name="id" value="{{ readthrough.id }}"/>
    <div class="control">on page</div>
    <div class="control">
        <input aria-label="Current page" class="input is-small" type="text" name="pages_read" size="3" value="{{ readthrough.pages_read }}">
    </div>
    {% if book.pages %}
    <div class="control">of {{ book.pages }}</div>
    {% endif %}
    <div class="control">
        <button class="button is-small px-2" type="submit">Go</button>
    </div>
</form>