I am a big fan of Vernor Vinge and I just re-read his Peace War series (two books, the Peace War and Marooned in Realtime, with a mini-book The Ungoverned in between). A great read- plenty of new ideas, action, characters.
Vinge introduced the concept of a "bobble" - a man-made, inpenetrable, indestructable mirrored sphere in which time stands still. Bobbles can be used as offense or defense, and wars involving bobbles can take hundreds of thousands of years. He is also one of the first (I believe) to talk about "the Singularity", in which "the creation of superhuman artificial intelligence will mark the point at which the human era will be ended, such that no current models of reality are sufficient to predict beyond it." Scary, but feasible.
The whole series is availale in a single book, so get started on it! Some characters follow through into another series, in Fire Upon the Deep and A Deepness in the Sky.