I get asked that question, from time to time (especially at the end of the year when I share that I've read x number of books, 78 in 2017).
And interestingly, I notice that at the start of every year I see a bunch of posts/articles claiming to have the secret to how you can read more.
Here's the real secret: there is no secret to reading more.
You just have to make time for it. You know that time you spend doing something other than reading for pleasure? If you spent that time reading instead, you'd read more.