I received a lock screen notification that Apple has many books for children and adults free for a limited time.
Some notable titles include:
Toy Story: Woody's Aqua Adventure
The Monster at the End of This Book
Another Monster at the End of This Book
How to Be a Grouch
The ABCs of Cookies
If you are trying to manually find the entire selection of free books:
1.) Open Books app
2.) Click on "Book Store"
3.) Under "Featured Collection", swipe to "Free books for everyone, from kids to adults."
4.) Select from the categories: "Love Sesame Street?, Explore dozens of free books", "Kids will be glued to this read-along book", "Picture books inspired by the Elephant Queen", and more