Halo War's is a great game for both Halo fans and fans of strategy games. It takes place 30 years before the very first game, exploring the war between the UNSC Marines and Alien Covenant.
It's also the first T rated game, as the violence is less graphic then the games released before.
The game is actually kind of simple. There are different "slots" around the map that you can capture from computer controlled factions ((Human Rebels/Forerunner) and use to build bases. Then build buildings in more slots, using them to upgrade or build units.
The campaign is pretty solid, with a decent plot and varied objectives.
I cant say anything about the online game though, as I dont have it.
Overall, a decent addition to the Halo franshice.