hook_pre_get_posts.php

<?php
add_action( 'pre_get_posts', 'wphc_modify_orderby_books' );

function wphc_modify_orderby_books( $wp_query ) {
	
	if ( false === $wp_query->is_main_query() || false === $wp_query->is_post_type_archive( 'books' ) {
		return;
	}
	
	$wp_query->set( 'orderby', 'title' );
	$wp_query->set( 'order', 'asc' );
	
}