Reading anything outside of the classroom is able to stimulate the child and continue to increase their curiosity for knowledge. Take for example when the Harry Potter series was first introduced. It gained popularity because children were attracted to this sense of magic. The public's love for this series helped maintain it alive and see it through to its completion, as well as see a follow up, "Harry Potter and the Cursed Child," to the beloved series.
For now some of the more popular and possibly easier readings to entice children would be the Marvel or DC Comics. Children relate to characters that fulfill their imagination and hopes for their dreams. When the Avengers movie first was released boys were dressing up as Captain America, Iron Man, or Thor. As lighter readings, at the most 20 pages for one issue, the ideas involved are a lot more complicated and it gives a child the possibility to comprehend the bigger plot by slowly engaging with the reading.
Yet, you may be thinking "Well, comics are good and all but what if my daughter does not relate to any of these popular super heroes?" Recently, Marvel and DC Comics have begun to incorporate more importance on the female audience. Thanks to new makeover by Babs Tarr, Batgirl has been getting more love and attention by fans, especially young girls. Marvel has seen the same with Spider Gwen and the new Iron Man, Riri Williams.
While a child may not know specific themes or words, just sitting down with them and letting them ask questions about the story will help the child grow. It can also become a pastime between the child and parent.