For reading in the dark on the Kobo Glo or Kobo Aura HD, use this simple hack -- it lets you easily invert the screen when reading in the dark (dark background, light letters). I love it. It is NOT supported on the Aura (non-HD); you CAN use it on the Touch and Mini, although neither of those have backlights:
https://www.mobileread.com/forums/sho...d.php?t=212162
Works flawlessly, easily, and makes night-time reading a joy; my favourite Kobo feature. (I have ALL the models listed above, but because of this hack I use my Glo much more frequently than I use my Aura -- I recommend a Glo rather than an Aura for night-time reading.)