This topic has been around many times before, but I was just sitting here and letting my mind run over it again.
The "How do I create a purpose" or the "What is a good purpose for this chapter" question came into my mind. Oten, when I was going to school I didn't really appreciate the course until it was review-for-exams time. Only then did the book (course material) come together.
Reflecting back on all those courses, I recall three basic types (there may be more). The first is the survey course, where you are just given a bunch of stuff to learn for that vague "later". Sometimes all these part actually fit into a whole picture / model / body of learning.
The second is where that vague "later" is at the end of the course. You are thought a bunch of tools you'll need to understand / do the really good stuff at the end of the course.
The third is where you go through the course and slowly build a more and more detailed understanding / model of a subject.
My suggest for reading a text book is to look at the objective of the "course" first. Then try and figure what the "textbook's author's" objective was. Sometimes they are the same, often they are not.
Once you have a feel for these, consider how each chapter helps to fulfill this / these objectives. This can help you figure out what you Want and Need from the chapter.
Now to be really general. I found that first year courses are of the first type. I would say that these are the hardest to form meaningful goals for. I would suggest, that you figure out why you Will Need or Will Want this information in the future. Seeing how this material will help you reach your goals will make it easier to create effective purposes. Hopefully your goals are not just "pass this course" or "get this degree" because you will have a life after those goals have been achieved.
Remember there are no bad goals / purposes. There are only good, better, and more better. The stronger you are interested and excited about fulfilling the purpose the more effective it will be.
You are perfection.
Iam2 