Rick Riordan has added another spin-off series to the realm of Percy Jackson... and it's fantastic! Despite this being the second spin-off series, the world of Percy Jackson never gets old. I read the Heroes of Olympus books as they were coming out, when I was about 10, but now I'm 16, and I still really enjoy them!
The Hidden Oracle follows the disgraced god Apollo, who has been cast off from olympus and thrust into the world as a mortal teenager with no powers by his father, Zeus, as punishment for his role in the war with the Giants. This brings me to this: if you haven't read Percy Jackson and the Olympians and The Heroes of Olympus, this book will spoil those ten books for you.
I really enjoyed The Hidden Oracle. Apollo is hilarious, shallow, and vain, and it's a joy to see him attempt to navigate life- a mortal life- without the very things (i.e. his powers, his eight pack) that made him Apollo. The plot is fun, and Apollo as a narrator is very enjoyable. If you liked the Percy Jackson series at some point in you life, even if you're my age or older, you should definitely give The Hidden Oracle a read!
Check out The Hidden Oracle on Goodreads here!