Edited August 3, 2017
at 07:44 AM
Amazon has several of their "National Geographic Readers" books at a discounted price. Prices start at $1.39 for "Storms" [amazon.com]
Shipping is free for Prime Members or at $25.
I ordered "Cheetahs" last week on sale for $2.xx & it's now down to $1.72. I just ordered the Alligators and Crocodiles one now and received a $1 digital credit at checkout when choosing no rush shipping. Edit: Just ordered Penguins & Dolphins as well - all in separate orders & got the $1 digital credit on each.
I didn't check Walmart, but Amazon & Walmart usually match each other on these types of deals,
I apologize for not individually listing each book... I don't have the time atm.
Link to all [amazon.com]