I have yet to re-read The Last Olympian at the time of writing this review, but as of right now, I think The Battle of the Labyrinth is my favorite book out of the Percy Jackson and the Olympians series. We see a tremendous amount of character growth in Percy, Annabeth, and Grover. The book (as well as the entire series but this book really hones in on it) really dives deep into idea that we are all propelled and/or haunted by the sins and choices of our parents. This book brings up big questions like: Will we outrun our fate and our parents mistakes? Can we be more than our parents' worst attributes and ambitions? We see this especially prevalent in the characters of Percy, Nico, and Annabeth. The book also starts to explore the idea of depression and grief in children and how this can fester and spread when left unchecked. Riordan plants the seeds for a much larger discussion in The Battle of the Labyrinth that he then dives deeper into in the series after this one, The Heroes of Olympus, where we meet Nico again.