This entanglement of the reader is, of course, vital to any kind of text, but in the literary text we have the strange situation that the reader cannot know what his participation actually entails. We know that we share in certain experiences, but we do not know what happens to us in the course of this process. This is why, when we have been particularly impressed by a book, we feel the need to talk about it; we do not want to get away from it by talking about it - we simply want to understand more clearly what it is in which we have been entangled. We have undergone an experience, and now we want to know consciously what we have experienced.
You will need a little background here. This is from Wolfgang Iser, whose stuff I'm slowly read at the moment (and it's a much pleasanter activity than I thought it would be). He's trying to describe what happens when you read a piece of good literature and he arrives at the conclusion that you get entangled with it. What does this mean? Well, a successful literary text will first draw you in under the guise of the familiar. You think you have an idea of what's going on in it, of where things are going. (If you don't have any idea at all, engagement with the text might be too difficult for you to even bother. See most readers and Finnegans Wake.) You inevitably form some expectations, some preconceptions based on your background, culture, previous experience etc. And then a good text challenges those expectations. In one way or another, things just don't go exactly as you anticipated. And this happens again and again in the course of your reading, as you form new expectations based on the new stuff the text throws at you. (Which is very good, because if this didn't happen, you'd have a yawn-fest on your hands.)
So what happens when you read a good book is that your preconceptions are continually overtaken, and, as you let go of them, you start to experience the text itself. The book becomes your present. You don't just read it, you become entangled with it and changed by it. That is the magic of good literature and it does make sense that you would want to understand it by capturing it in words. It makes sense you would want to share it. But it also makes sense that you'd fail at this task. You can't really capture the sense of living in the present of a book. If you're very good, you can give someone a wonderful representation of what it was like to experience a book, you can explain what elements in the book allowed for this experience, but you can't give them the experience itself. That's why you end up sending them to the book instead.
But another interesting corollary of this is that you can't really have access to that experience either. You can remember what it was like to read a text, but you can't read it again and have the same experience. Just the fact that you now know how it ends will change the way you read it, will change your preconceptions and expectations. (The text can still surprise you, though.) So I guess that, if we accept all this, no man (or woman) ever reads the same book twice.