Every time I launch Lightroom photo book I get this error message sfntread library error.

Hi there,

Thanks for reaching out. We are sorry about the trouble with the Book module in Lightroom Classic. We are here to help!

This issue could occur if Lightroom Classic cannot access fonts that are corrupted on Windows. It is recommended to check for corrupted fonts and add them again until Lightroom works. Refer to the article below to troubleshoot fonts. 

https://helpx.adobe.com/x-productkb/global/troubleshoot-font-problems-windows.html

You can also try resetting Lightroom Classic's preferences and caches by going to the following locations and renaming the following folders by adding .old at the end. (Folder > Folder.old) 

Please close Lightroom Classic before starting with any troubleshooting steps.

Go to these locations and rename only the 'Preferences' folders as 'Preferences.old'

• C:\Users\{userName}\AppData\Local\Adobe\Lightroom\
• C:\Users\{userName}\AppData\Roaming\Adobe\Lightroom\

Relaunch Lightroom Classic to check for any differences.

Please let us know if this works! 

Regards,

Sameer K