Rick Riordan also has two more series that tie into the story line you are reading now. The first is "The trials of Apollo" which is a spin off kind of sequel for the story line your on now. Main character in this one so far is Apollo. The next is a Norse mythology line of books "Magnus Chase and the Gods of Asgard". The main character in this series is Annabeth's cousin.

Both of these series are turning out to be as entertaining as the omes you mentioned above. I rather enjoy how all these series tie into one another. Reminds me of Stephen King's Dark Tower series in that aspect.