So, you're a fresh reader. Your vocabulary is not as extensive as you'd like it to be yet, you struggle with terms and objects and places in other countries/planets/dimensions, and you're not familiar with terms like Bildungsroman, Grandfather Paradox, or foil character. Do you only go with the books you understand now, or do you pick something that looks interesting but will be difficult to get through? Of course, there are people who stay the way they are and only go where they see fit. Like a co-worker of mine. He'll struggle to spell the word "sci-fi", much less put himself through a whole book of it. So he instead sticks with books like these:
True to the Game
Shaqeesha's Baby: The Trilogy*
Straight From Da Hood, Yo*
Memoirs of a Crackhead, as written by the person he stole them from*
Get Off My Government Cheese!: The Prequel*
Rick James, Bitch!: The official biography of the Bitch Rick James was talking about.*
*not real books
These are Urban books, or "Hip-Hop Literature" as Wikipedia would call them. And to add to what I put above, there are plenty of people that read these things because they want to, and not because they can't read anything else. With that said, these novels often appear absolutely idiotic to me, but to each their own.
I remember seeing things like the Lord of the Rings books selling millions of copies (at the time of the film release) and wanting to read it before the film came out, so I borrowed the trilogy from a friend. I could not, for the life of me, make heads or tails of what the hell was going on in certain parts. I'm a person that envisions what I read, and so all the passages with environment and nature talks of this kind of tree and that ridge above this creek drew blanks for me. If I were my other co-worker, I would've given up and stuck with being entertained by stuff like Max Tucker. But this didn't make sense.
Contemplating putting the book down made me feel like I couldn't go on to anything else because I quit that one. "It's too hard to read, no one's going to like this./But millions of people have already read and enjoyed it, so what are you missing?/well, what did they understand? Did they understand?" And it's not about the book itself, but the feeling like my intelligence has limits.
This was when I first started taking literature seriously. I eventually finished the book(s) and went on to other stuff that looked like it would challenge me. I've never wanted to just stay with what works for me. you imprison yourself in ignorance that way. I wanted to be able to read anything from classics to sci-fi to espionage. From a Doctor who trades his soul for mastery of the Dark Arts, to a boy playing in his poor Venezuelan park, to a CIA agent getting permission from Quantico to dig up files about a secret Indo-Vietnamese War.
My point is that I think it's better to make the mind adapt to the literary world, not to just stay with what you know. That's no good. Books are supposed to teach you, not tell you what you already know.
This same thing goes with writing. If I imagine something, I want to be able to portray it as realistically and accurately as possible in words. Note: realistic does not mean imitate the surface of life (only what meets the naked eye). It means the components of your story must interact with each other as they logically would given the totality of whatever properties you create for them. Whatever disorders and powers you give to somebody or something, you must imagine, in detail, how life would be for them. So, do not, as so many people have stupidly done, have a character suddenly be able to cause earthquakes or read people's minds and just go straight to thinking about how to use these powers without first being shocked that such powers exist.
At any rate, the truism of reading or writing what you know holds true, but that doesn't mean to only stick with what you know. This is pride in ignorance at its finest. Anything that you want to write about, you get to know. Any word you don't know, you look up. Reading maybe difficult for you now, but it's only because your mind is being cultured and your interests are widening. Many people have said this and I don't remember which or who, but "intelligence is the refining or strengthening of the soul". In researching, you may find that whatever work you're approaching goes deeper than you thought.