This is a very good game which lets you take control of 10 spartans instead of 1.
The only downfall is a minor one as you get used to it. It's on the xbox 360 instead of pc. You'll completly forget that once you go through the tutorials. It's also quite hard to see where units are on the map so once you send them out in the wilderness, it's quite hard to make them return!
The storyline isn't the clearest ever. You are the UNSC and you are trying to stop the alien invastion from the covenant. Lots of units from the original halo series like the grunt and the scorpion make an appearence aswell as new arrivals like the wolverine and the flamethrowers.
Overall, if you like rts games or you are a fan of the halo series, this is a must have.