I have just finished reading the book "Halo:The Fall of Reach" by Eric Nylund. It is about a boy called John (also known as The Master Chief) and how he grows up as a Spartan (not the old ones in 300) and how the UNSC ( United Nations Space Command) battle against the ferocious Covenant, which is an alien race. The setting is in the year 2517 to the year 2552.
If you are familiar with the Halo games, you will know the terms the book uses. (Yeah, people who don't play Halo are totally clueless about the terms used in the book.)
The Covenant are an alien race which intends on wiping out mankind. One of them looks like this:
Yup, it looks totally freaky. I recommend this book to anyone interested in science fiction, war or technology.