Old Man's War
I've always found the huge white space on Goodreads reserved for a review after reading a book quite daunting. Here's an attempt to fill one:
I've found this book fascinating mainly because of two things. First, it deals with those eternal questions we humans probably had ever since climbing off of trees. It's as much a philosophy book as science fiction. Neil Gaiman wrote in an essay about ideas that a great way to come up with them is to ask questions: Old Man's War has sprung from really gripping ones.
Second, the way it's been put together. It has those sentences that, once you're familiar with the context, hit so right home it's stupefying. Maybe that's literature: words strung one after another in a way they imply a world beyond. It borders magic.
There're also spaceships and aliens, of course.