Which book series from Rick Riordan do both the fantasy novel The Hidden Oracle and the Camp Half-Blood-Chronicles have in common?
The Hidden Oracle: The Hidden Oracle is a fantasy novel based on Greek and Roman mythology written by Rick Riordan. Percy Jackson &amp; the Olympians: Percy Jackson & the Olympians, often shortened to Percy Jackson, is a pentalogy of adventure and mythological fiction books written by American author Rick Riordan, and the first book series in the Camp Half-Blood Chronicles.
i don't know