It used to happen to me a lot that I used to sit in front of the book but my mind used to be somewhere else. Like what is the whether outside or what will be cooked for dinner tonight or why is melody so Chocolaty :p. This was becoming a huge problem.
Then my mentor suggested that I should keep a record of the time I take to read a chapter. I used to write the start time and finish time on top of the starting of each chapter. This worked wonders for me. I was able to finish entire chapters in a matter of minutes and no distracting thoughts occured to me.
Also, you could solve questions instead of reading text if you think you are unable to concentrate. Because questions automatically make you think more as a higher % of cerebral cortex in involved.
Some people like to hear music when they read. you could follow that technique but I advise you to listen to only instrumental music instead of vocal because it causes less distraction.