Amazon has released a new version of its Kindle app for iOS, which has been updated with X-Ray for books. The feature — which had been exclusive to Kindle hardware until it was introduced for textbooks on iOS in late October — provides a useful graph that highlights all mentions of characters, places, and concepts throughout the entire book. For more information on a given topic, X-Ray points you to Wikipedia and Shelfari, Amazon's literature-focused community encyclopedia. After marketing X-Ray as a unique selling point of its Kindle devices, Amazon is now working to push the feature to other, more universal devices in an attempt to sweeten its content ecosystem. The free, updated app is available for download now in the iTunes app store for all iOS devices.