* "Antidisestablishmentarianism" (10 syllables) - This is the classic example, a very long and complex word!
* "Incomprehensibilities" (8 syllables) - Another long and challenging word.
* "Interconnectedness" (6 syllables) - This is a more modern example of a lengthy single-word title.
Ultimately, the "winner" depends on your definition of "book title" - are we talking about titles that have actually been used, or theoretical titles?
Let me know if you have any other word-related puzzles!