I read Magnus Chase 2: The Hammer of Thor recently. I liked the book, and I'd say it's just as good as the first one. There are two new characters, unless they were in the first book, and I forgot about them. The first is Amir, the person that Sam is engaged to. He's in the process of learning about the Norse mythology stuff, and he is rightfully FREAKING OUT. That type of character can be annoying, like in Indiana Jones 2, but it works here, because Magnus knew Amir long before the mythology stuff ruined their lives.
The second new character is Alex, who is a shapeshifter and also transgender. That was a really neat idea. She can change forms into whatever animal she wants, but her own personal identity is fluid, so she can never quite match it or keep up with that. An interesting conflict, to be sure. However, at times, the author gets a little TOO heavy-handed with the issue of supporting transgender rights, to the point where it feels like he's preemptively calling you a transphobic bigot if you ever disagree with a transgender person about anything ever. Or maybe I'm just a touch oversensitive to those issues, because I occasionally get a lot of grief for being a male who plays female Nancy Drew games.
The story is typical of the Rick Riordan books. Our heroes have to fetch a magic item that the gods have somehow lost. There is kind of a clear road map they have to follow, from A to B to C, but they keep getting tangled up in random 50-page sidequests that focus around a particular mythological character. These include challenging giants, visiting Hearth's evil father, going to Thor's house, and so on. The overall story is that they have to get the skofnung sword and wheel, so they can trade it for Thor's lost hammer at a wedding.
Towards the end, the book talks about Norse wedding traditions. The dowry goes to the bride's father, not the groom's family. I thought this was setting up for a big plot twist at the end, because of who Alex's parents are, and how they technically don't fit the tradition as described. (I'm trying not to give spoilers, here.) But no, I was wrong, that ended up not being important at all. Okay, then. I fail at foreshadowing!
The book goes on for several chapters after the dramatic finale, which I thought was very well done. I particularly liked that. I didn't like the final cliffhanger, which was "OMG, Percy Jackson is going to get involved in this story!". That's not the first time we've seen this end-of-book cliffhanger from Rick Riordan...Still, it was a neat book, and I'll definitely read the next one in the series.
I wonder what mythology Riordan will tackle next, after Egypt, Greek, Rome, and Norse. Like, Lloyd Alexander and J. R. R. Tolkien already wrote AMAZING series based on Welsh mythology, and it would probably be impossible to do Christian mythology while having it still fit in with the pre-established Roman mythological canon that Riordan has developed. (Plus, it'd be hard to do Christian mythology without offending a TON of people.)