Currently Amazon has Summer Bridge Activities on sale for 32% off- these are a great to keep kids on track for the upcoming school year! Most grade levels are currently on sale for $10.11 each and shipping will be free at $25 or with Prime.
Also check out Amazon's 4 for 3 section several more Summer Bridge Math & Reading books can be found at $8.95 each. Pick 4 and the price drops down to $6.71 each and shipping will be free with Super Saver shipping!
Thanks to Savings Lifestyle for the tip!