I used to read many books when younger. Maybe four or five a week. Earlier this year, I realised that I was down to three or four books a year. I also had trouble reading longer articles. My years of web browsing and skimming had retrained my brain to only look at small amounts of text before moving on. I did not like this. So I started a programme in my life. If I came across a longer article on the web, I forced myself to read it in full. Man, that was hard at first. I had to force myself to complete this many times, until it became a habit. It also made me realise that not all long articles were crap.
Then I turned to books. I started reading again. Start with smaller fun books, and persevere till they were done. Note them, write small book reports for myself, and keep going. Almost one year later, I am reading a book a week. I will continue this and hope to increase back to two books a week.
Self-discipline is what did it for me. I am sure that there are many other ways of approaching this and changing your own behaviour.