His villain can do no wrong, perfectly predicting the reactions and behaviors of dozens of humans so that his impossibly convoluted master plan goes off without a hitch (until the climax, anyway). His writing is stiff and swimming with exposition and lectures, and if you've read any of Brown's other novels the plot twists are completely predictable.
Still, it's a fairly light, easy read; the 500+ pages went by pretty quickly for me. It'd serve reasonably well as an airplane/beach book.
But the story is ruined by silly, haphazardly constructed aliens and gaping logical inconsistencies. The extra-terrestrials have godlike physical and mental powers but are easily duped with regards to THEIR OWN RELIGION by a painting and a puppet show. The president is an ethical, shrewd, benevolent man but allows people to be publicly kidnapped and tortured largely because they're political opponents.
The ending is absurd. The Fresco is a disappointing waste of potential.
It served as an excellent exercise in what one can learn from examining both sides of a disagreement. A surprise thumbs-up.
It's urban-fantasy-meets-old-fashioned-private-eye-noir, kind of a cool combination. Green is a little too smug and self-aware to be really good though; the protagonist is supposed to be tough and dangerous but he usually just comes off as a poser.
The author uses too many superlatives, like Pratchett but worse. Every other character is the baddest, deadliest, evilest thing to ever walk the Nightside. It gets old.
But it's not a bad book; I found it to be a fast-paced and fairly amusing. It's just that it doesn't live up to it's potential.
Unfortunately "Something from the Nightside" is also very self-conscious. Literally every other page contains the sentence "[Something bleak and ominous], in the Nightside." Green reminds the reader of how "other" his creation is, ad nauseum. I get it, the Nightside is ultra-dangerous, and the hero is proportionally amazing; stop treating me like I'm stupid.
But in spite of the distractions and occasional insults to my intelligence, I found it to be a fast and fun story. I'm looking forward to the next book.