This version has a number of fixes (thanks Kabutak for the issues you spotted). I have also added a similar feature to the Fantastic Fiction plugin allowing you to choose whether to retrieve the first published date (default) or the specific edition date for a book.
I think I also remembered to remove the debugging code this time, apologies for those who tried and failed with the last version...
Give this one a whirl, if it gets a thumbs up I will update the first post so everyone can easily get it...
(EDIT) New version that ensures the default is "true" for first published date, for the one person who downloaded you may want to go in and turn this option off/on to ensure you see the same
