Amazon just updated its Kindle app for iOS with its “X-Ray” feature, which lets readers quickly get background information on characters, places and other aspects of the book they’re reading.

X-Ray debuted on the company’s Kindle e-readers, but it’s the first time the feature has been rolled out for one of the company’s apps on another device.

As a typical use case, Amazon cites the example of George R.R. Martin’s “A Dance with Dragons,” which has more than 400 characters. A reader encountering a character who was last mentioned 2,000 pages ago can tap on the X-Ray button in the app to get a quick rundown on the character’s background and see excerpts from previous mentions.

The update, released this morning, is for iPhone, iPad, iPad Mini, and iPod touch.

Amazon also makes apps for platforms including Android and Windows, but the company isn’t yet providing any specifics on plans to roll out the feature to additional Kindle apps.

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