Allow each book to use its own preset

[jim_chapman]

As a quick update - I'm still encountering the issue on a day to day basis. To alleviate the pain I'm keeping Freda app open as long as possible, but this seems to reappear quite consistently these days on each app restart.

I'm considering to delete all my books and reinstall from scratch to try my luck at some point, oh well...

I do have a new release coming out in the next few weeks, which changes the code so it takes more care to avoid concurrency issues when loading and changing settings.  That might help your situation.