Amazon offers Madeleine L'Engle's The Wrinkle in Time Quintet Boxed Set for $10.99 with free shipping for Prime members. (Target charges the same with in-store pickup.) That's the lowest price we could find by $17. It includes A Wrinkle in Time, A Wind in the Door, A Swiftly Tilting Planet, Many Waters, and An Acceptable Time.

Update: Note that this item is temporarily out of stock, but can still be ordered at this price for delivery when available.