There are many different themes throughout both books! An example would be: arrogance can lead to vulervibility of preeation and a lack of prepreation. This means that mankind thinks : 'oh there are no Martians, what?! Yeah no way are Martians going to land on Earth, why waste money and supplies to stock up and train for something that will never happen!' So when the preperation lacks, then mankind is a easy target or very vulerable.