1. First, open the book app on the iphone or ipad, as shown in the figure below.

2. Enter the Book app and click the image to log in, as shown in the figure below.

3. Then log in to the same Apple ID account in the open window, as shown in the figure below.

4. After logging in successfully, ibooks in iphone and ipad are book apps, and the data in the stacks will be synchronized. Today's reading progress and reading goals will also be synchronized.