Bruce Banner (The Hulk) has been exiled to the planet Sakaar by, who he thought were, his friends. Iron Man, Reed Richards, Dr. Strange and Black Bolt are soon going to have to deal with the repercussions of such an act as Bruce has made his way through the gauntlet on Sakaar and has become King. His revenge will be their undoing as he brings his Warbound to Earth to pay back what was done to him.
Not having read Planet Hulk, I wasn't sure I would be able to dive straight in to World War Hulk, but I was mistaken. You are given several glimpses into the past (though the exact reasoning behind his exile is still a question) to see how Hulk has gained his new power and the respect of his Warbound. There is plenty of violence and super-heroing to go around, but the story feels a little clunky in some parts. Also, the background storyline of the Sentry gets slightly old and annoying but ends up being a nice little joyride.
If you enjoy beautiful artwork and tons of Hulk-y violence, World War Hulk is for you. Especially if you think Tony Stark and his bros deserve to be tossed around and bloodied for a time.