Harry Harrison - Deathworld (version 2)

A world that actively seeks to kill the colonists. Not a pleasant place. The hordes of ferocious animals all come with deadly poison and a will to kill as many humans as possible. Even the plants have teeth and claws and toxins dripping from every surface. They fly, crawl and run for the chance to sink something terrible into a human arm or leg. Oh, and did I mention the 2G gravity? Pyrrus is it's name. The settlers there were supermen… twice as strong as ordinary men and with instantaneous reflexes. They had to be. For their business was murder...a 3 year old Pyrrian had a loaded gun strapped to his forearm and knew how to use it or he was a dead 3 year old.
It was up to Jason dinAlt, interplanetary gambler, to discover why Pyrrus had become so hostile during man's brief habitation...if he could stay alive long enough to even make a start — Summary by phil chenevert