Please don't unterstand my comments as pure and overall critique; if one hasn't any experience in the field, never done any prototyping before, this person might learn something here.
But for all who read the Bill Buxton "Sketching User Experiences" book, worked with paper-prototyping before and probably lots more this workbook is superfluous. Too much pages describing "techniques" like tracing photos to get better proportions...
I expected a lot more, at least some things to learn or new, something original. But I got a lot of links to other books and line tracing, wow.
Save your bucks, get other books.