Firing a Ctools Modal on a link click
You mentioned you tried ctools_automodal which is a quick way to accomplish creating a link in a view to open in a modal. With the module, you can use hook_menu_alter to add 'modal' => TRUE to the link menu router item. Nothing else is involved. Ctools_automodal handles all the rest. That means you don't need your own example_modal_page page callback, and you don't need to call ctools_modal_render. Let the Ctool_automodal module do that for you.

If your path has a wildcard, then ctools_automodal will need an actual wildcard variable defined and a "_load" function. In your example above, your path is selectbook/%. If you change it to "selectbook/%selectbook" and defined a selectbook_load function then ctools_automodal should recognize it as a modal path. Here's an example:

/**
 * Implements hook_menu().
 *
 * The sole item call in hook_menu is driven from a URL that is built
 * from rewrite rules within a view. When activated, it should render
 * the new modal window.
 */
function example_menu() {
  $items['selectbook/%selectbook'] = array(
    'title' =&gt; "Perk Modal",
    'page arguments' =&gt; array(1),
    'page callback' =&gt; 'example_modal_page',
    'access arguments' =&gt; array('view content'),
    'modal' =&gt; TRUE,
  );

  return $items;
}

function selectbook_load($selectbook) {
  // Todo: Do something with selectbook, like load an entity.
  // For this proof of concept, just return it.
  return $selectbook;
}

function example_modal_page($selectbook) {
  // If you loaded an entity in selectbook_load, then you have that
  // fully loaded entity in $selectbook.
  return "Test Modal";
}