Seach the forum I've written a lot on purpose. You'll find that it is a personal thing.
What you need to consider is, Why are you reading this"
'Teacher says I have to" Great, the answer your mum always gave you when she told you to do something. Why? "because I said so or else." Not a great motivator was it? And you got the 'or else" more often than you care to remember. The problem was no purpose. The because I or someone said so never was and never will be the motivator.
Then there is the other times when you had a purpose for doing something and the results were less than brilliant. Your experiment failed and instead of pouring the milk into your cup you managed create the milky puddles and you are pulled up in front of your elders (parents, teachers older sibling doesn't matter who). 'Why did you do that'. Your motivator was you wanted some milk and you wanted to do it yourself. The purpose "to pour some milk so that I can have a drink."
So you told them that, and you get this lecture even nicely said, it bites, you're too small, ask for help,think things through. Worse if you happened to cop a scolding and sent to your room. Not only are you miserable that your purpose failed but you got in trouble for it too.
Kids learn fast. Next time you get caught doing something daft, when they ask you "why did you do that? I don't know (actually you had this brilliant idea and you tested it. Your purpose was to do this ..... so that I can see what happens when...). You get the lecture anyway but shortened the agony of explaining yourself. Lets you get away from the confrontation faster.
The Problem with your answer "I don't know" it becames the automatic response to the question "Why are you doing this". Why are you reading this book... "I don't know." So the answer is simple.... don't read it. You don't need to. "But I have to read it." "Why?" "because the teacher said so."
Here we get stuck because we need to uncover the teachers motive for wanting you to read that book or a reminder why you are taking the class.
If you want to find your purpose make a list of possible grains or benefits you would get from reading the book. Look at the title and come up with some ideas. Deside which gain particularly motivates you at this point in time with the book
Now you have something for a purpose statement, you have the why you are reading the book. The purpose statement (the "why" you are reading this book) '[i]I am reading this book on... by... so that I can [potential/expected gain].
After an activation or two you might discover more potenial gains that's fine it might mean you have an addititional purpose for the book.
Alex
[This message has been edited by Alex K. Viefhaus (edited November 10, 2004).]