(major spoilers below)
Light Bringer is a bit of a course correction after the Iron Gold and Dark Age flops. Quicksilver and The Figment were ditched. Sevro was quickly freed from imprisonment (without any brainwashing). The Abomination was barely mentioned. Volsung Fá and the Ascomani turned out to be frauds and not real threats (Darrow defeated them in a day without an army). The story went back to Darrow and his friends against the baddies, and that is a good thing.
Lysander doesn’t work as a character. Brown wants to tell a villain origin story from the villain’s POV, but the villain is an emotionless, vanilla character who never garners an iota of reader sympathy. Lysander is boring and his many betrayals are predictable.
It was obvious from the get-go this would be Cassius’ redemption story. He rekindles his bromance with Darrow. He bonds with lowColors. He makes amends with Sevro. His beauty and fighting skills are brought up ad nauseam. So it’s unsurprising when his death comes, as his arc was wrapped up nicely.
The obviousness of Cassius’ death could be forgiven if he didn’t die for such a stupid reason. Lysander has shown us who he is over and over again. There are no redeemable qualities. Only a fool would trust him. Cassius being that fool takes away from the emotional impact of his death. There were attempted explanations for this — Cassius was Lysander’s mentor and saw him as a sort of replacement for his late brother Julian. It’s just not enough of a justification to forgive Cassius’ stupidity.
Overall, the book was only OK. It’s still riding the coattails of the original trilogy. That’s fine with me. The more Darrow and Sevro content I get, the happier I’ll be.