1. Change the country and region of the Apple ID account.

Turn on the iPhone or iPad, go to Settings, iTunes Store and App Store, click the logged-in Apple ID account, enter the View Apple ID option, and switch the country/region to the United States or other countries. Then open the iBooksStore and it will be displayed.

2. cancel the Apple ID account.

Open the settings of iPhone or iPad, click iTunes Store and App Store, click the logged-in Apple ID account to log out, and then log in again.

3. Disconnect and reconnect the network.

Open the settings on the ios device as above, input the Wi-Fi signal, ignore this network, and then try to reconnect. You can also turn on other network signals, and then open the ibooks store to see if it is back to normal.

4. Restore network settings

Click the Path button of Settings, General, Restore, and Restore Network Settings, and then restore.

5. Redrawing system

The Ibooks store is unavailable, and sometimes there may be a problem with the ios system. Just restore the ios system settings, click Settings, General and Restore, and select "Erase all contents and settings" in the restore menu bar. This setting will delete all data in the device, so you'd better back up some important data before performing this operation.