The underlying issue has been fixed in Markster 3.0.9.

If you've updated to an earlier 3.0.x version and already had the crash, you can either

(a) trash the Logs files as described in my previous post, and then once you've got Markster running, click in the main menu: Markster > Check for Update to get the latest fixed version, or

(b) Download the latest fixed version from here and then, using Finder, trash your old Markster.app and replace it with the fixed version.

Thank you for contacting us.  Another user reported this issue and we are working on it.  We also have a workaround which worked for this other user:

• Activate Finder.
• Click in the menu: Go > Go to folder.
• Copy and paste the following "path" into small text field which appears:

~/Library/Application Support/BookMacster

• In the window which appears, select the three files

Logs.sql
Logs.sql-shm
Logs.sql-wal

(It is possible that you might have only one or two of those.)

• Drag them to your Trash.
• Retry to launch Markster.