When you click on the "Collections" tile at the left of your lobby, you'll find ten "Locations" there with different themes. You need to collect 10 unique items for each location to be filled. Every card has its own star rating; the higher the star number, the rare the card is.
After completing each book, you'll get a completion bonus, and when you complete all the books, you get a Grand Prize!
Tap on 'Collections'