Board Thread:General Discussion/@comment-3542839-20140227002012/@comment-4763787-20140705163957

Crim2003 wrote: If Riordan used the real seventh as an answer, then it would ruin the final surprise. You need to think as writer to understand it.

But how do we know that Annabeth not being one of the Seven is the final surprise?

Well, messing up with the reader is his favorite game. Everyone thought that Percy was the hero in PJO series, and he was not, so, we know that Riordan has the mention to turn the things we think on reverse.