I am not getting the total number of pages on apple books

First make sure it is not a audio book if that failed try restarting the app if that did not fix the problem try doing a hard reboot (steps below)

1. Press and quickly release the volume up button.
2. Press and quickly release the volume down button.
3. Press and hold the side button.
4. When the Apple logo appears, release the side button

if all other options fail try deleting the app and reinstalling it

If that doesn’t work, try contacting Apple support