To download and purchase books from the iBooks Store, you'll need an Apple ID. To read PDFs and ePub documents accessible on your applications, you'll need to check in with your Apple ID on the iBooks Store. Here's how to use the iBooks Store to download and purchase books:

1. Open the iBooks app to get started.
2. Then go through the books in the Featured or Top Charts pages, or use the search option to look for a specific title.
3. To learn more about a book, simply tap it. You may also read reviews, look up comparable titles, or browse available sample pages by tapping Sample on the right side of the screen.
4. When you've made up your mind about buying a book, tap the price on the side of the screen.
5. Then choose Buy.
6. To receive a free book, go to the right side of the screen and hit Get, then Get Book.
7. To discover a book you've previously purchased or to acquire the most recent edition of a book you already own, tap Purchased at the bottom of the screen.
8. Read more