I read this book in one sitting last night. It's not terribly long, but more importantly, it's a page turner. So engrossing.
I don't want to give much away. You should go in blind, if you can.
Suffice it to say that this is a science fiction novel. Mostly, the book is two characters on opposing sides of a war writing letters to each other. It is thrilling. It's heart wrenching. It's profoundly romantic. I heartily recommend it to you, at least if you enjoy sci-fi.
Time War is one of my favorite books of all time, I think