Old Man's War, by John Scalzi
The book is about a future earth, which is packed full. There are colonists on other planets, but the only way most of earth's population can join them is by first joining the army (colonial defense force). The only catch is: you can't join the army until age 75.
Although I've known John for quite some time, and I enjoy dancing with him, this is the first of his books that I've bought. I'm mildly ashamed of that fact -- although I have at least read another of his works online (Agent to the Stars).
It turns out that not only is he a fun dancer, he can write a good story as well! This book captivated my attention from the start, and I really enjoyed it. I liked both the characters and the ideas, so it was an excellent read.
I have to say I was a little disappointed with how it ended, but that didn't ruin the book for me by any means. The book was entertaining -- definitely recommended.