Well there was more than one book left. Krako said there were other books that showed them how to make radios and such.(Im assuming architecture and the like as well, maybe some films also)) Of course we didnt see the whole planet so we dont know what other technologies were being used. Plus Spock and Kirk have seemed to land in the heart of the gangster culture since Krako was the one with the book.
As Spock said the Iotians are an very imitative people. So maybe they were obsessed with getting it right.
But I find its still a silly ep no matter how hard I try to put logic to it. Still its great fun to watch. "Concrete Galoshes" still makes me laugh to this day.
Spock, Scotty and McCoys attempt to act like gangsters per Kirk always gives me a smile. Kirk was the only one to get the lingo.
