The Reader view in Safari has been one of my favorite features in iOS and in iOS 9 it has been updated to provide more options for customization. Not only can you adjust the text size, but you can also choose from four (4) different backgrounds and select different fonts including the new San Fransisco iOS 9 font.
The Reader feature behaves in a similar way to how it did in previous versions of iOS, in that you access it by tapping a special icon on the left side of the browser’s address bar which will only be visible when you are on a website/blog that supports this feature (usually news sites and other sites that update frequently).
Once you are in the Reader view, which removes a lot of the extra content (such as site navigation and many ads) you will now see an additional icon on the right side (big A and little A).
Tapping on this icon will reveal a popover with text and background options that are now available in iOS 9.
I have posted a short video on my YouTube channel that shows the iOS 9 Reader view for Safari in action:
The Reader view is great for not only removing a lot of the clutter on a page to make it easier for learners to focus on the content, but also for making it easier to use some of the accessibility features such as Speak Selection (the built-in text to speech feature of iOS).