I just finished Godsgrave and oh boy I have so many things to say.
The gladiators part was fantastic, I'm biased but Kristoff has done a good job depicting the brutality of it and the ecstasy that came with victory
For the saga "every side character is more compelling than Mia" we have too many characters: Leona was amazing, Bladesinger and Wavewaker have the coolest backsotries and I think Furian deserves more space (just to name a few)
Matteo is the only pure character in the series and he last like three (3) chapters (Jonnen could maybe compete, but he was still raised by Scaeva so we'll see)
Mia is still the lamest character of the series, she has more plot armor and is more unbelivably good than a shounen protagonist, to the point of going against common sense when you know what she's been through. She is good for the sake of the plot (and Kristoff reminds us of this with bringing up the end of the previous book multiple times)
The plot twist of Mia being the daughter of Scaeva became obvious when she dicovered that Darius had a lover
And last, but not least, Scaeva appears and in one single scene became, hands down, the best character of the series
Now I'm left with only Darkdawn to read