If the Now Reading plugin is causing a problem, then I’d suggest not using it.
CG-Amazon does pretty much what that Now Reading plugin seems to be able to do, but allows for more than just “books”. You can define an arbitrary number of things in the CG-Amazon interface (by using the Amazon ASIN number or a search function) and then display any given set of those things by Amazon Category, your own categories, etc. It can display them randomly, in order, etc. You can control the size of the image, or not display an image, whatever. Very easy to use. Also uses your Amazon affiliate account ID so that the links generated will earn you some minor cash.
CG-Amazon is one of David Chait’s plugins, over at https://chait.net .
I use it to display a random book on the side of my blog. I basically defined a bunch of my favorite books in the “CGA” panel that it creates, then I used an ExecPHP widget with this code:
<?php show_amazon_items(1, 'rand', 'Medium', '', 'Book'); ?>
This displays one random item, with a medium size cover image, from Amazon’s “Book” category (and ignoring my own categories). Easy, no?