Dispense with books! Be no longer dragged about by them! It is not permitted.
Ancient Stoicism did not belittle study, learning and inquiry. Quite the opposite, in fact. Another Stoic who lived earlier than Marcus, Seneca the Younger, at one point claims that he does not give himself rest and even allots a portion of the night to study. But a fickle and purposeless learning, a cusory jumping from one volume to another, is not permitted (that is, not useful or conducive) for the student who seeks to be wise. This kind of reading is especially prominent in our age of Wikipedia and the internet, combined with the double-edged sword of widespread literacy, which makes many fancy themselves experts in fields they have no real authority in.
Worse yet is the kind of excited (or bored) curiosity that leads one to read book after book for mere entertainment value, or the impressionable and rapid jumping from one school or doctrine to another while never gaining a meaningful understanding of any of them. The former kind of reading can only excite, not cure, the Passions; the latter is a symptom of an already unsteady mind.
How many of our novelists, both popular and literary, produce works that seem to make excuses for or even glorify the very Vices that the philosopher would flee! The poets in the time of Marcus Aurelius did this very thing, exploring and embracing - in poetic metre and flowery language - all that is base and fickle, rendering the Passions as something not ugly, but attractive. Our poets and song writers today do the same. Our writers seek in their works to touchingly capture and display the "human condition", but never to cure it. Instead, they aggravate our illness by placing before our eyes the entire range of human goods and evils, and, in our age of moral ambiguity, rarely distinguishing between them. It is impossible that we might intentionally expose ourselves to this onslaught of emotions our writers set against us and not be affected by it, not be "dragged about" by these Passions that we foolishly indulge in as entertainment!
Likewise, we allow ourselves to be "dragged about" when we roam aimlessness from one philosophical school or religion to another, learning quickly the basic slogans of each system but never truly understanding those systems and therefore never able to make use of them. To never change your mind when you discover you are wrong is to be a mule, not a man; but to change your mind on a whim, without serious deliberation (or for the sake of change itself!), is to be an unstable man.
The Stoic knows how to read books properly; he is diligent in his study so as to teach himself to not be dragged about by Passions, conflicting ideologies, and the conceit that comes from the cursory knowledge of a subject.