Amazon offers Prime members the LeapFrog LeapReader Deluxe Writing Workbook: "Learn to Write Letters with Mr. Pencil" for $7.99 with free shipping. (Non-members can spend $35 to bag free shipping; otherwise, it adds $6.48.) That's a buck below our December mention and the lowest total price we've seen. (It's a current price low by $3.) It features a 20-page story with 45 activities and 400 interactive responses. It works with LeapReader system (not included).
Note that this item will be in-stock on March 18; it's still orderable today.