The Forever War

I liked the writing style and the plot seemed promising. A war that has been going on for a thousand years against an alien race.

However, as with many war stories, it focus on the technical aspects of war that I do not find interesting. The book details the training of the troops, the special mechanized suit they had to learn how to use, the difficulties of training in a barely hospitable freezing cold environment. The unit the protagonist belongs to is the best there is, and still many are expected to die before training is over.

They're goal is to protect the portals from which instant travel to other portals in the universe is possible.