eroux

Supplying an <a href="https://en.wikipedia.org/wiki/International_Standard_Book_Number" rel="nofollow ugc">ISBN</a> (and, optionally, a Title) will display a cover image of the relevant book with a link to that book’s page on <a href="https://books.google.co.za/" rel="nofollow ugc">Google Books</a> using the Google Books API.
Using the Widget you can choose whether to:
<ul>
<li>Force all calls to Google to be HTTPS, instead of the API returned HTTP</li>
<li>Pad the Image (selected by default, uses internal CSS)</li>
<li>Display a Box-Shadow (selected by default, uses internal CSS)</li>
<li>Choose Alternate Google Country (defaults to “Worldwide”)</li>
</ul>
as well as
<ul>
<li>Decide whether you would like to use a Title</li>
<li>Define the ISBN-10 or ISBN-13 of the book.</li>
</ul>
<h3>Usage</h3>
<ol>
<li>Activate the Plugin via “Plugins” → “Currently Reading” → “Activate” (if you hadn’t already done so).</li>
<li>Go to “Appearance” → “Widgets” and drag the “Reading” widget into whichever Sidebar you choose.</li>
<li>In the “Currently Reading” widget, you can then customise it further.</li>
</ol>

Currently Reading

Displays a cover image of a book with a link to Google Books based on a supplied ISBN-10 or ISBN-13.

cmeeren

This is a “set it and forget it” widget which allows you to display shelves and reading progress from your Goodreads profile. You can add multiple widgets and configure them individually to show multiple shelves.
Some configuration options:
<ul>
<li>Large/small cover images</li>
<li>Message to display if shelf is empty</li>
<li>Sort books by reading progress, date updated, shelf position, author, title, etc.</li>
<li>Number of books to display</li>
<li>Display your rating</li>
<li>Show first line of your Goodreads review (intended for quick notes such as “reading this together with Alice”, “recommended by Bob”, links to reviews, or whatever else strikes you fancy)</li>
<li>Show reading progress bar, progress text (no bar) or don’t show progress at all</li>
<li>Display time since last update (e.g. “2 days ago”)</li>
<li>Custom strings for time since last update (e.g. for quick and easy translating, or to change “2 days ago” to “2 floobargles since last update”)</li>
</ul>
Almost all HTML elements have dedicated CSS classes to allow you to easily override the style. The widget looks OK on the most popular WordPress themes.
Requires PHP 5.4 or later (PHP 7 supported).
The source is hosted on <a href="https://github.com/cmeeren/gr-progress" rel="nofollow ugc">GitHub</a>.

GR Progress Widget

Widget to display shelves and reading progress from Goodreads.

Currently Reading vs GR Progress Widget