Disabled AJAX paging with embedded views when used in Views template files
It looks like you are adding some chunks of code logic to your theme templates?  This is not usually recommended in a drupal instance.  Have you tried adding a context to include your loadcover view block on the view generating your grid, so that you do not need to print embed in the tpl?
https://www.drupal.org/project/context

Enable the module and go to /admin/structure/context/add  Set the name of this context, something like Book Grid Display.  We use a "Layout" tag group for things like this, but you could use "custom" or just about anything you want, it is optional.  Under the Conditions dropdown select Views, and on the list that appears to the right check the box in front of your Inside grid view.
Under Reactions select Block.  The theme regions will appear as well as the different groupings of blocks available on your system.  The last grouping is Views, select your Loadcover view and click the +Add on the theme region you are wanting (I assume Content since you were printing this in the content template).

The page content will have a weight of 0, and the drag-and-drop reorder likes to start at weight -10 so use the Show Row Weights to get it under the view grid if desired.  Or at least that is a quirk I have seen when using this method.

Another note, the views_field_view that was mentioned in a comment would allow you to add your Loadcover view as a field in your book grid view, so that you did not have to inject it with custom code from the theme logic layer.  If you were wanting to invoke LoadCover for each cell in your grid and I missed that part, then yes views_field_view would solve the problem for you instead of this context solution which will get you one instance of Loadcover.