You have a book with .epub or .mobi format in your MacBook or PC.
You want to put it into your iPhone or iPAD so that you can read it on the go.
1. Put the books into iCloud Drive.
2. Install Kindle or Apple Books on your iPhone or iPAD.
3. Login your Kindle account.
4. Open the Files app to go to iCloud Drive.
5. Open the book.
6. Tap the Share icon in the lower left hand corner.
7. Select Kindle or Open in iBooks.
1. Install Kindle or Apple Books on your iPhone or iPAD.
2. Log in your Amazon account.
3. Point mouse to Account & Lists, then click Content and Devices link.
4. Click Preferences tab, then click on Personal Document Settings header.
5. Copy or create your Kindle email in Send-to-Kindle E-Mail Settings section.
6. Add your personal email to Approved Personal Document E-mail List.
7. Attach your book to an email, then send the email from your personal email (in the 6th step) to your Kindle email (in the 5th step).
8. Log in your personal email’s Inbox and click on Verify Request link.