Riddonkulous

What am I? Some riddles are short, some riddle are long, but all contain me. This riddle is the longest possible, no riddle has more of me than this one. It's beginning to look more like an essay than a riddle. Incidentally, essays have me too. In fact, every text in the world contains me. No matter how short or how long. Have you figured it out yet? It has to be said, it's really hard work to make a riddle that has the maximum of me. This riddle is getting so long, by now it's more like a book than a mere essay. By the way, have I told you yet that books also contain me? OK, we're almost at the end. Riddonkulous allows seven hundred and fifty of me, less if you are a novice. In the meantime, have you guessed what I am? Well done!!!