Apple won't allow you to delete built-in apps in regular ways. However, you can get rid of preinstalled apps from macOS by disabling SIP first and running commands in the Terminal. However, you should think twice since it's not easy to reinstall built-in apps once they are removed. Also, the removal of certain default apps can cause issues with macOS updates.
SIP (System Integrity Protection) is used by Apple to prevent the removal of necessary built-in programs. It essentially restricts what we are able to do to protected parts of the macOS, making it more difficult to uninstall programs on Mac. Although it's not as easy as removing third-party apps on Mac, you can follow the tutorial below to delete the Book app on Mac.
Step 1. Disable SIP from Apple Menu > Restart. Hold down Command + R key combinations to boot up your Mac in Recovery Mode. Select Utilities > Terminal and enter the following command:
csrutil disable
Hit enter and restart your Mac.
Step 2. Open Terminal from Finder > Applications > Utilities. Open your application directory by entering the following command and press Enter.
cd /Applications/
Step 3. Use the sudo rm -rf command to delete default apps. Since you want to remove Book, type in the command:
sudo rm -rf Book.app
Then press Enter to confirm the action.
Step 4. Once complete the uninstallation process, restart your Mac once again.
It's important to enable your SIP again. To do this, launch Terminal again, this time enter the below command instead:
csrutil enable
Similarly, you should restart your Mac once complete.
