Their similarity not lies in their looks, albeit both of them maybe share the same lean muscular physique. It is in their witty, sarcasm, and their tendency to insult higher authority that makes Magnus and Percy almost identical. Their sidekicks are no different either. Blitzen the dwarf remind us with Leo Valdez. Hearthstone the Valkyrie is Jason Grace. Samirah Al Abbas the valkyrie is an hijaber version of Piper MacLean. Feels like Riordan attached trio from Lost Hero to a blond version of Percy Jackson. Worse, Annabeth still in the story. Magnus is Annabeth’s Cousin.
The first part of Riordan’s Norse myth story highlighted his inability to come up with different characters, or simply to develop them. His avid readers would know exactly what would happen to the characters next, or their next move. Even some readers got a sense that he wants to keep his fans loyal, by giving them other version of their beloved characters. He don’t want to gamble his newest story with really really new characters or unpredictable storyline.
My opinion: Riordan must bet new characters development and new storyline to his next book (Thor’s Hammer). Loki ain’t Kronos, Magnus not Percy, and Hearth definitely not Jason. Its better if Riordan add some twist to their personality (no, not twist to their background) so those new characters doesn’t look like carbon copy of Heroes of Olympus’s.