Campbell: The upgrade can be taken by folks certified in Java 6, 7 or 8. So it is certainly reasonable for the reader to be new to lambdas.
Mikalai: We did that for our readers. THe intro has a mapping that covers what chapters of the book they have to read for the 817.
Mohana: No. You don't have to read the entire book. The intro (page liii-iv maps the 817 objectives to chapters in the book. Lambdas are covered in chapter 12 (pages 520-527). They are also covered in part 1. But reading chapter 12 is sufficient to learn what you need for the upgrade exam as far as lambdas go.