The master cheif, as said by katsoyori, just doesnt like the thought of death. The only reason he does it is because he thinks he can save the lives of more humans by killings the cov. I think that if he loved to kill do much, then he would have shot the arbiter in the face when he had the chance in halo 3. But no, he worked with the arbiter and the elites. Even the games show that. And as for his lack of personality in the games, i think bungie was too busy making the awesome gameplay and the graphics and well, maybe they just forgot that little part as to his personality. I personally own all 5 books, but not because i am obsessed with halo; they are just great books. Although Ghosts of Onyx didnt focuz on the Master Cheif as it did the spartan II's, you still get that sense of adventure when you read the books. The halo games were well made, are fun to play, and have, and will always have, one of the coolest main characters to ever be genetically modified to super-human standards, survive two alien ring worlds infested with parasetic life forms, and to drive a jeep into the hanger of a launching spaceship in order to escape a third ring with his life and the life of an alien warrior.