How I read 3 different genres (textbook ,facebook,email)

When I read a textbook I focus myself on learning the subject which is presented in the textbook. In contrast to that when I read a facebook message it is all about getting to know what the person want to tell me about hisself or some activity he wants to do. I feel familiar which the facebook message because I know the person I am writing with and in a textbook it is not like a conversation it is like a lecture in class where only the teacher talks about a topic. The third genre is emailing. It is a kind of in the middle of this two because it depends on with whom you are writing. You can write with a friend like on facebook or you write with your professor and it is formal and it is sometimes only a one way conversation like in a textbook. But you have the possibility to answer to the email, so you can change the one way conversation.