I have the Clarke/Crisp book too, Alexandra (the one with the hideous orange cover, right?). The only other book I have that might be considered any sort of history book is The Simon & Schuster Book of the Ballet, which is really just a catalogue of ballets starting with the Ballet Comique de la Reine. Great descriptions where possible, but doesn't attempt to say anything about the various periods.
I think "Imperial Ballet" is the perfect name for the time of Petipa



