The Bio-Mech War, Book 5: Blue Iguanas

An existential war between biologicals and mechs. In the near future, scientists discover a flickering artificial sun headed towards Earth. Code named "Deimos", this alien threat becomes the impetus for a massive outworld colonization program, the creation of an army of mechs to defend the planet, and a bioengineering initiative to adapt the human race to survive the apocalypse. All of these projects are kept secret from the civilian population, including the orphan Junior Rangers they depend upon. When Thuy steals a hand blaster, the Junior Ranger Program is devised to dispose of lunar orphans. On the current mission to a world with kilometer-tall forests, Junior Rangers find platforms in the trees and a nomadic species of reptiles. When Thuy falls to the swamp below, he must use all of his skills to survive. As he tries to fit into iguana society, and get back to the colony, Thuy is shadowed by a mech who has other ideas.