Jist! is a free, lightweight extension that allows you to read a short summary of any block of text on a web page - articles, emails, fanfictions, you name it. All you have to do is highlight the text you want summarized, click the extension icon or context menu item, and get the Jist!
Check out Jist! on the Chrome web store: https://chrome.google.com/webstore/detail/jist/fbldjpeagfenapjgkilmnlmflbfbefhe