This was a good book because it ties in with the XBox and PC games(that I have played).
It tells the story of the Spartan 2 programe and the fall of the great planet Reach. Reach was where the Spartans were brought at the age of 6. They get given special armour(which you will see in my album of Halo).
They and the UNSC (or Earth) are fighting against the Covenant a mix of alien races (again see the album Halo on my profile).
When Reach falls under attack the Spartans must go and help defend it some go to the ground and some in space under the orders of Master Chief the leader of the Spartans(see album).