What really works for me is an app called Marvin 3 on the iPad. I read them on the train for a total of an hour a day.
It works for me because it reads the books for me (text-to-speech) while I read along. This blocks out the surrounding noices in the train and the lack of internet on trains (I prohibit myself from using my phone’s hotspot on the iPad) keep my attention at it for far longer. And when you set it to a higher pace, you’re forced to keep your attention at the text, otherwise you get lost (for example 2x or 2.5x in the lower right corner).