Someone posted on the busy board a few days ago that scholastic is having a sale on class sets (20 books for $20). I ordered the calculator riddles for my students and got them a calculators from the dollar store as well. It's a really fun book and I ended up spending only $2 per kid!
I have ordered gift certificates from Scholastic. They are $1.95 a piece and are good for any book $3.95 or less. I used bonus points for the purchase. My plan is to give the class a copy of the January form, let each child choose, and order them over the break.