I guess everybody here just has a looser definition of cheating than mine. If he were asking for suggestions on books with good characterization, then that would be okay, but actually giving him the passages goes a bit too far for me. When I'm writing a paper, my teachers expect me to 1)do the research myself, 2)examine the research to see how it will help in my paper, and 3)expand on it in the actual paper.
Maybe that's just my school and Dangerbutton did say he's looking at other books as well, but if his paper were just about Mistborn then you guys basically did #1 and #2 for him, 2/3 of the assignment. Granted, the teacher can only see #3, but #3 is supposed to show how well you did #1 and #2.
Of course, if the teacher said "Dangerbutton, write a paper about characterization and ask as many people as you like to find examples of characterization for you," then this would be okay, but since he/she probably didn't say that I would call this cheating.
And yes, Wielder, I think having a book with all the main points highlighted would be cheating as well. Not the kind of cheating where you ask someone to summarize the book for you, but the kind of cheating where you didn't do all the work the teacher was expecting of you when he/she gave you the assignment.
Some teachers might not care, but there are others who want you to learn by following all the steps in the process and not by working on only the last step.