I read a few posts here and around the Net saying that a user would turn off System Bright within the Kobo Library App and STILL would find the 'Auto Bright' function working to turn up or down the back-light intensity after they exited the Library app. For instance, they would see their back light intensity change on the home screen as they handled the Vox at different angles.
This is true. If you want to set the System-Wide back-light intensity to a user setting, you need to go into SETUP and then tap on the DISPLAY section. There, you will find the true System Brightness check-box and/or the intensity slide bar for your own setting. It is this setting that affects all the other apps and your home screen.
What the Vox in-house Library screen brightness setting does, is to let you adjust for that app only. As soon as you exit out, you are now running under whatever setting you set the system-wide brightness setting to be. Either auto/system bright, or your personal setting using the same control
I just thought to give this head's up.