The Trials of Apollo, Book Two: Dark Prophecy
Oh, Apollo. Lester (aka the pimply teenage version of Apollo) finds himself in Indianapolis with Leo and Calypso. Their search for the second emperor Commodus (the Commodus of Gladiator fame) has them teaming up with two old acquaintances of Apollo. They need to free two griffins, find (and heal) a missing girl, and receive a prophecy from Apollo’s foreboding son. All the while, they have to stop an attack on the demigods’ safe haven. Of all of Rick Riordan’s characters, Apollo/Lester is the wimpiest one of them all, but he still manages to save the day. 
