Heavy Object is the new work of the creator of the Index/Railgun franchises, and as to be expected, it's truly good. The story takes place in the future, in an era where flesh-and-blood-soldiers wars are a thing of the past. The battlefield is now controlled by monstrous machines known as "objects", which are gigantic and so indestructible that nuclear weapons are no match for them. The strength of countries are now measured as the number and strength of the object possessed, and soldiers no longer fear the battlefield since wars are fought between this terrible weapons of mass destruction.
The protagonists of this story are Quenser, a student that hopes to be an Object designer in the future and Heivia, radar analyst. The two of them are thrown into an unexpected crisis, and to survive they'll need to destroy the enemy object after theirs is annihilated. Could they, a mere flesh and blood soldiers, defeat a 50-meters-and-100,000-tons monster that cannot be defeated even with nuclear weapons? Can they, armed only with their wits, courage and a bunch of low-powered explosives and weapons which would not even scratch the paint of the monster change the way war is made forever and the first ones in the history of humanity in defeat an Object, a creation that can destroy an entire country in a matter of minutes?
The only thing, however, this manga fails is that it's only one volume long and it merely adapts ONE CHAPTER of the original novel. Like you read, the entire manga ONLY adapts ONE CHAPTER of the entire story. So as you may expect, the whole manga is merely a kind of introduction of the story and is merely a kind of prologue to the whole world of HEAVY OBJECT. If you want to read the complete story, I highly recommend reading the Light Novel, which Baka-tsuki is presently translating and releasing in a surprisingly fast pace. The day this comment is being written, they have just released the complete volume one, which I seriously recommend you to check it out.