-After each post that is a news article, can i call up the book posts that relate to the same category somehow?
Use the Category Widget or template tag, wp_list_categories(), in your sidebar to present a list of categories that when clicked will take you to all the posts in that category.
I would like something that will show products relevant to the post (same category) at the end of the post.
A related post plugin will do that or this code:
Display posts belonging to the categories of the current post without duplicating the present post
<?php
global $post;
$cat_ID=array();
$categories = get_the_category(); //get all categories for this post
foreach($categories as $category) {
array_push($cat_ID,$category->cat_ID);
}
$args = array(
'orderby' => 'date',
'order' => 'DESC',
'post_type' => 'post',
'numberposts' => 8,
'post__not_in' => array($post->ID),
'category__in' => $cat_ID
); // post__not_in will exclude the post we are displaying
$cat_posts = get_posts($args);
$out='';
foreach($cat_posts as $cat_post) {
$out .= '<li>';
$out .= '<a href="'.get_permalink($cat_post->ID).'" title="'.wptexturize($cat_post->post_title).'">'.wptexturize($cat_post->post_title).'</a></li>';
}
$out = '<ul class="cat_post">' . $out . '</ul>';
echo $out;
?>
Related:
Stepping Into Template Tags
Stepping Into Templates
Template Hierarchy
Here's another ecommerce plugin and the author does a good job of 'support': http://wordpress.org/extend/plugins/eshop/