The Riddle Book (aka Rare Book) was a rare book, because it hadn't been out in the sun too long.
Background[]
The cover was worn, and Alexander could only make out that it was called, "The <something> <something> Riddle Book" on the binding. The cover only has the letter 'R'.
He browsed through it and found that a page was missing. Though he found the answer to the riddle had blown into Black Widow's web. Ali accepted the Rare Book in trade for his magic book.
Riddles[]
The page containing the 'love' riddle, was between a riddle about an 'olde black bark tree' and another with a jester. The love riddle is the riddle that Gate would later ask Alexander in the Land of the Dead.
Behind the scenes[]
This is known as a 'Rare Book' in the KQ6 hintbook.