As I said above that is with no authors set, you can see it in the log where it says:
Running identify query with parameters:
As per the log you originally posted the plugin did the right thing by connecting directly to the url for the goodreads id as per this part of your log:
Goodreads book url: u'http://www.goodreads.com/book/show/588334'
The line underneath where it says "Could not find title/authors/goodreads id" is indicating that in attempting to scrape that URL above it could not find sufficient of title/authors/goodreads id to qualify it as a valid title. Perhaps you just had a blip on the internet which gave a dodgy web response back. Certainly it is all working fine for me so unless someone can post a scenario to replicate I'll let this one slide.