In custom post type book I have several books published
I just want to show data obtained from metabox field but I have not been able to help me the code that I am showing does not work

   <?php $book=get_post_meta( get_the_ID(), 'name_ebook', true ); ?> return name ebook Paintree

            <?php 
                $loop_args = array(
                 'post_type' => 'book',
                 'order' => 'ASC',              
                 'meta_key' => '$book',  
                 'orderby' => 'meta_value',
               ); ?>

show only search Paintree ebook