Conversation so far:
who's the actor that plays percy jackson
Logan Lerman is an American actor, known for playing the title role in the fantasy-adventure Percy Jackson films.
are the percy jackson films based on books
Percy Jackson & the Olympians is a feature film series based on the novel series of the same name.
who is the author of the percy jackson and the olympians novels
Percy Jackson & the Olympians, often shortened to Percy Jackson or PJO, is a pentalogy of fantasy adventure novels written by American author Rick Riordan.

Question: when were the novels published
Self-contained rewrite: when were the percy jackson and the olympians novels published