I've seen a bunch of tweets recently asking various questions about boys, specifically, and reading. As a boy, with two grown sons, I figure I am qualified to respond, at least generally.
I never had any trouble. I read early and often, as the saying goes. Voraciously. Fiction and nonfiction, biography, history, mystery, and adventure all were consumed almost as fast as I could take new books out of the library. But them I've seen the other side. Boys who refused to crack a book. Who balked at doing any homework that involved reading more than a couple small paragraphs.
Until, that is, the boy found something that interested him. Interested him enough to make it important for him to read instead of run outside and play baseball, or video games, or watch TV.
That, I think is one crux. In our society, for boys, these other things are often valued more than reading. For girls there is not as much social stigma, inside their peer group and from parents, to spending time reading. We do our boys a disservice, in general.
However, there is another side; a biological side. This thing our brain does converting spots of ink on a piece of paper into intelligible language is a thing that requires the pathways that are linked to genes, many of which are sex-linked. Dyslexia occurs with a much higher frequency in males than females. It is hard to explain to the non-dyslexic how difficult reading is; how difficult learning to read is; if you are dyslexic.
For the dyslexic (I have several examples in my immediate family) it is a very difficult thing to learn to read. It is painful, especially in the light of others learning the skill with apparent effortlessness. Once you have adapted, once you have built those pathways painstakingly where genes would have built them seamlessly, then you have the opportunity to find something interesting.
So it is a triple problem - interest, social pressures, and genes. The first is easy - plenty of exposure to many genres and styles. The second is an evolutionary process which we, as parents and advocates, need to encourage, as we need to in many areas, the removal of gender as a criteria for one preferred behavior over another. The last is out of our immediate control except for the patience, encouragement, understanding, and assistance we can give to make the process shorter and less painful.
Me as a critic (be careful! the harshness will be well concealed!)