Better grid loop for secondary query

template-books.php

<?php

/** Template Name: Books **/

add_action( 'genesis_after_post_content', 'be_list_posts' );
/**
 * List Posts
 *
 */
function be_list_posts() {
	$args = array(
		'post_type' => 'books',
		'posts_per_page' => -1
	);
	$loop = new WP_Query( $args );
	if( $loop->have_posts() ):
		echo '<div class="book-listing">';
		while( $loop->have_posts() ): $loop->the_post();
		
			$classes = 'book one-third';
			if( 0 == $loop->current_post || 0 == $loop->current_post % 3 )
				$classes .= ' first';
			echo '<div id="book-' . $loop->current_post . '" class="' . $classes . '">';
			the_post_thumbnail();
			the_title();
			echo '</div><!-- .book -->';

		endwhile;
		echo '</div><!-- .book-listing -->';
	endif;
	wp_reset_query();
}

genesis();