What makes a good book?

Why are cartoons valued less than books? This is one question I asked myself as I read Show and Tell for class this week. The comic itself stated "real books" were ones with "no pictures at all". That got me wondering, if a comic or graphic novel tells and intense and meaningful story, is it still not considered good literature? The fact that this comic is in an AP English Textbook is a contradiction to that statement, it was considered good enough to be in something that teaches children about literature. So is it rather the content that places what good literature is? Children's books, the ones we used to read in like second grade about mysteries and adventure, while having no pictures, are not considered real books. Because they have simple language and are 100 pages or less, they are deemed for children, not adults. So, is the language and word choice make a real book? Show and Tell used somewhat high diction words, maybe not too complicated but enough where just anyone wouldn't be able to read and understand it. Now, I know that this is just my useless rambling at this point but, does elitism have something to do with good literature? The fact that a book has a lot of pages or complicated word choice so that only fairly educated people can read it, seems like an elitist complex. Only smart people can read this, to prove we're better than others kind of concept. I don't think it's right, anyone should be able to enjoy good literature no matter their educational backing. We should judge good books based on content and original thinking, the implementation of morals. Not just on how smart it makes us look.