Actually, I fixed it! When you changed the capitalization issue in the code, the single.php was still looking for a capitalized "Books".
Correct code:
<?php if(get_post_type($thepost) == 'books'): ?>
Actually, I fixed it! When you changed the capitalization issue in the code, the single.php was still looking for a capitalized "Books".
Correct code:
<?php if(get_post_type($thepost) == 'books'): ?>