Books are written works. They can be any length and be concerned with any subject. Some are just pictures; some are just words. Some have both. Some have neither. Almost all were written by people. They can be electronic and meant to be read on a computer or tablet or they can be printed on paper made of mashed-up trees. You can even make one yourself! There have been books for about 2000 years. Before that, people wrote mostly on scrolls and clay (i.e. non-electronic) tablets.
The act of decoding the information and ideas in a book is called reading. Without reading, a book is just an inert thing. As an object, a book might be heavy or light; if some books fall on your head it could hurt. Book-related accidents and instances of violence involving books are pretty rare.
Historically, the only people who have considered books dangerous are people who want to limit the diversity of ideologies or information available to a population. Some famous examples are Nazis, Puritans, school boards, prison administrators, New York's Governor Andrew Cuomo, and parents. When the population for which the book is banned is a group of children, the most common reason for the ban is that the book contains an idea at odds with the banning party's conception of its social mores, such as references to the universal human interest in sex. When other populations are the ban's subject, such as citizens of a fascist regime or prisoners, the motives are more commonly political. Such attempts to limit the spread of ideas are rarely successful, and in many instances simply result in heightened interest in the banned book. They are probably more successful in prisons.
There is, however, some inherent danger in exposure to new ideas. Primarily, this danger is that you might adopt a bad idea as your own. If you read a lot, you're likely to develop some reading skills and perspectives that minimize this danger. We're not too worried about it—we'd prefer that you read anyway. Just remember to think!
On the whole, we do not consider books dangerous and, honestly, question the motives and values of anyone who does.
