This is doable in a simple way with a bit of PHP and JavaScript.

First, you need to set up The “ebook” and “audiobook” variations as virtual products:

Then the following code will (for virtual variations):

• Set the max quantity to 1 (in product page),
• Hide the quantity button (in product page),
• Hide the quantity button (in cart page).

The code:

// Product page: Set max quantity for virtual product variation
add_filter( 'woocommerce_available_variation', 'wc_available_variation_max_qty', 10, 3 );
function wc_available_variation_max_qty( $data_variation, $product, $variation ) {
    if ( $data_variation['is_virtual'] ) {
        $data_variation['max_qty'] = 1;
    }
    return $data_variation;
}

// Product page: Hide quantity field for virtual product variation
add_action('woocommerce_single_variation', 'variable_product_jquery_script', 5);
function variable_product_jquery_script() {
    // Enqueued JavaScript
    wc_enqueue_js( "$('form.variations_form').on('show_variation', function(event, data){ 
        if( data.is_virtual ) {
            $('div.quantity').hide();
        } else {
            $('div.quantity').show();
        }
    });" );
}

// Cart page: Hide quantity field for virtual product variation
add_filter( 'woocommerce_quantity_input_args', 'filter_wc_quantity_input_args', 10, 2 );
function filter_wc_quantity_input_args( $args, $product ) {
    if ( $product->is_virtual() ) {
        $args['min_value'] = $args['max_value'] = 1;
    }
    return $args;
}

Code goes in functions.php file of your child theme (or in a plugin).

In single variable product page (physical product variation):

In single variable product page (virtual product variation):

In cart page:

Based on: