The Sword of Summer

The first thing anyone wonders when they know Percy Jackson but not this series must be, "So weird that Magnus' surname is the same one as Annabeth's." Yeah, OK, that's because they are family. And I don't think it's such a big spoiler to say that Annabeth does have her own small role to play. Until now, this is really the first actual reference in Riordan's book series that they are set in the same world and age (not counting the short stories of Percy, Annabeth and the Kanes). The second thing I noticed was that there was a chapter in which he names Jason Grace, which makes me wonder what will happen in the other four books. (He already revealed that Annabeth will appear more than once.)
Riordan sort of turns his back to the 'Heroes of Olympus' books because in 'Magnus Chase' he just uses a singular I-character (Magnus, of course), like he did with the Original 'Percy Jackson' novels.
Apart from Magnus - he's fantastic - there's my ultimate favourite for this series (it took me about one paragraphs, even before her name was said): Sam. She is so enormously wonderful. I really don't know how to say what I'm thinking - in my opinion, she's one of those kick-ass heroines of this time.
So, the Gods of Asgard. Those are the Norse ones. Probably one of the things that I love about Sam is that she is a Valkyrie - I mean, can you imagine it: women, chosen by the highest god to reap dead men's souls who died a hero's death, with their weapon in their hands. Just one of my favourite mythical 'humans'. In fact, I just like the entire mythology, I don't know why. It really speaks to me and the images it puts in brain when I'm reading about it are amazing. An enormous tree that encompasses nine worlds!
And even if you're not all that interested in the Old Norse myths - oh my god, just try this one. Riordan is a master weaver of stories, and he doesn't drop a stitch here.