Colonization: Second Contact by Harry Turtledove

Harry Turtledove's Colonization: Second Contact opens, two decades have passed since the Lizards invaded Earth during World War II and an entire generation has grown up without knowing a world in which the Lizards have a presence. Rather than being the fearsome enemy, they are now hardly stranger than foreigners and have a strong effect on fashion. Sam and Barbara Yeager's son Jonathan, for instance, has shaved his head and dyed his skin in imitation of the Lizards. However, world leaders such as Premier Molotov, Fuhrer Himmler, President Warren and Fleetlord Atvar are concerned that their tentative truce is about to explode into open warfare once again when the colonization fleet passes within the orbit of Mars.