Your can use post_parent
parameter for your query.
Ref: https://codex.wordpress.org/Class_Reference/WP_Query
This will change your query to:
$args = array(
'post_type' => 'b_books',
'order' => 'ASC',
'orderby' => 'date',
'posts_per_page' => 10,
'post_parent' => 0
);
genesis_custom_loop( $args );