Pomodoro.

You can do just about anything for 20 mins. So set a timer and read for 20mins. Then you get to stop. Then set another timer and take 20 mins off. Then 20 reading again and so on.

One you are in the groove with that, then you reduce the off-time to 15 mins, then 10 and finally 5 mins - so 20 mins reading and 5 mins break and repeat.