Three stars because I really like the premise and the focus on science BUT, (1) as with the first book, the author dedicates one story line to a boy, and as with many US authors, kids can't die even if it would make sense in terms of narrative. Also, somehow, here as well, a boy is the big solver of the plot. That's just uninteresting and boring. And, that boy drugs up and kidnaps a woman who just happens to be petite and drags her to become part of some creepy harem and can't understand when the woman later does not treat him like a hero. Pass me the barf bucket.
(2) There is a lot more focus here on a small group of rangers + one sniper. Said sniper cannot do anything without being reminded of some awful stuff he'd done in Brazil. And so, like Rose Nylund in the Golden Girls, constantly repeating "back in Saint Olaf", It's almost as if Leo is constantly going "back in Brazil". This gets repetitive and tedious.
I am also sorry that the main character of the first book takes a back seat in this one.