This is a book club membership with first set free
Here is part of the T&C
"Submit your order today, and we'll send you your first four books in the National Geographic Kids Readers Program absolutely FREE! You pay just $1.00 for shipping and handling.
If you are pleased with your first 4 books do nothing and in about three weeks and each month thereafter you will receive 4 more books from the National Geographic Kids Readers Program for just $3.99 each ($15.96) plus $3.99 shipping and handling and plus sales tax if applicable. You are under no obligation to continue. Your credit card will remain on file and all future shipments will be charged to the card unless you notify National Geographic otherwise."