I don't have an answer for you, because I have been looking at this for my son too. However, CBD.com has the set for $27.99, that's only a couple of dollars more than the student book alone. I would say go for the set :)
http://www.christianbook.com/jump-in-kit-2-volumes/sharon-watson/pd/437014?item_code=WW&netp_id=461233&event=ESRCG&view=details