I'm a F.lux user, it dramatically improved my life. With that frame of reference, I've had no sleep issues from my iPad, which I use to read before bed most ni

I'm a F.lux user, it dramatically improved my life. With that frame of reference, I've had no sleep issues from my iPad, which I use to read before bed most nights. In fact, I read in lower light using the ipad than with a conventional book and lamp on the nightstand. The two main apps I use are iBooks and the Kindle app. Both apps have controls for turning text white-on-black, and controlling the brightness. At night, I read exclusively white-on-black at low brightness. Additionally, for apps that don't support inverted text, you can bind hitting home three times to invert the colors. Its at Settings -> General -> Triple-click home.