Another new book has been published about OpenCart:
Here is the description:
Customize dynamic menus, logos, headers, footers, and every other section using tricks you won't find in the official documentation
A great mix of recipes for beginners, intermediate, and advanced OpenCart template designers
Develop and customize dynamic, powerful OpenCart templates to make your website stand out from the crowd
Fully customizable administration theme for OpenCart
You can purchase the book here:
This book goes quite indepth on customising opencart, of couse you need some basic PHP and HTML skills.