I am getting this now in the latest update.
crash-2020-06-08_03.43.10-server.txt

Looks like a Linux server specific error with the config file writer.
I've tested it on windows where it had no issues. Will fix that, sorry about it.

Here to report the same issue, this only happens when launching a server.
The desktop where I run it has Windows 10
crash-2020-06-14_18.41.07-server.txt

LostBooks-II-1.12.2-2.0.1

Fixed, release is now on curseforge
25be66d