How to switch to "Reading View" mode in Internet Explorer 11 on Windows 8.1

The modern Internet Explorer 11 on Windows 8.1 provides a reading view for a more streamlined, book-like reading experience of webpages, without the distraction of unrelated or other secondary content on the page.

Reading view is a view of IE11 in the new Windows UI that, when available for a given webpage. Reading view clears away the clutter-like ads-so stories are front and center.

To switch/leave to "Reading View" mode
If the webpage supports reading view, then you can tap or click the icon "Switch to reading view" (book icon) to open the page in reading view.

When you want to get back to browsing, just tap or click the icon "Leave reading view" (book icon) again (or with Ctrl + Shift + R).

To customize your settings for reading view

• Swipe in from the right edge of the screen, and then tap Settings.
  
  • If you're using a mouse, point to the lower-right corner of the screen, move the mouse pointer up, and then click Settings.
• Tap or click Options, and under Reading view, choose a font style and text size.

Note: This feature is not supported in IE11 on Windows 7, or Internet Explorer for the desktop on Windows 8.1.

References:
Windows integration
Getting started with Internet Explorer 11
Introducing Reading View in IE 11