When I click om "Book" in LR i get an error message "sfntread library error". Other modules work fine.
It could be a bad font installed on your computer. Try quitting Lightroom and all other applications and re-start your computer. Then re-launch Lightroom.
I tried this but now I get the same message when opening LR
The only other suggestion is to trash the prefs which will return them to default. See link below. If that makes no difference you made need to uninstasll, run the CC Cleaner tool and then re-intall LR6.0 followed by the 6.10 update.