It must be said that I read a lot of children's books. For many years that has even meant picture books (I still read those - a good book, is a good book!). Now, though, it's mostly upper elementary and junior high level. There are several reasons for this.
One is that I like to preview material for my kids to see if it's something that I either know or hope will interest them. Or to check if the content is "suitable".
Another reason is that when checking out a new topic of interest for myself, often reading a book that is geared to younger children will explain it in simpler language. You can get the big picture first, and then go on to the finer details.
And then sometimes the book just has an appealing storyline - no matter your age.
These books have their place. There comes a time, though, when you must read at a deeper level. Here's where Bloom's Taxonomy can help out.
Benjamin Bloom came up with a structure of "knowing levels", from the basic knowledge level through comprehension, application, analysis, synthesis and ending with evaluation. Different groups over the years have used his levels for their own purposes, such as teachers making exam questions. But they can be helpful to individuals who are intent on self-education as well. After you have become familiar with the facts in an area of self-discovery, challenge yourself with the higher levels to see how much thinking is going on. You don't just want to be able to win a place on "Are You Smarter Than a Fifth Grader?" or "Jeopardy". You want to have a relationship with the people you are reading about. You want to know why they behaved the way they did, what the implications of their behavior were and ultimately, you want to see the hand of God moving through history.