If the Read Me app is missing from your Xiaomi phone, here’s one way to get it back:
- Go to this thread at MIUI forum, and download the userbook.apk file to your phone.
- Once it’s on your phone, tap the file and follow the on-screen instructions to install it.
- When the installation completes, you should see the Read Me app in the Tools folder.
- Now, you can tap the Explorer app > MIUI > userbook to check if you have the manual downloaded before this, if you can see a manual_xxx_xx_xx_xx_x.xx.zip and a folder with the same name, that means the manual is already on your phone. Simply launch Read Me in the Tools folder and start reading.
- If you see an empty userbook folder then that means you don’t have the manual yet. Launch Read Me in the Tools folder will prompt it to start downloading the 20MB zip file. For this approach, you need to connect to a fast Internet connection, and you can enable Show connection speed in the status bar to ensure the download is progressing. Note: It took me more than 20mins to download the Mi 3 user guide. I actually left the Read Me app “loading” with the screen set to never timeout. Also, I tried a different service provider when I failed to do it with the first one.
For this approach, you need to connect to a fast Internet connection, and you can enable Show connection speed in the status bar to ensure the download is progressing. 
Note: It took me more than 20mins to download the Mi 3 user guide. I actually left the Read Me app “loading” with the screen set to never timeout. Also, I tried a different service provider when I failed to do it with the first one.Have any other method to reinstall the Read Me app on your Xiaomi phone ? Share it in the comments.
Note: The steps here were written for a Xiaomi device running MIUI V5. If you’re having a different version of MIUI, there’s a possibility that the steps and screenshots will be different.