Iain M. Banks - Consider Phlebas
The first novel in Banks's highly-regarded "Culture" series. I've been meaning to jump into these books for a while but when you look at them all stacked up next to each other the book store, all those thousands of pages, it can be daunting. Banks is known not only for his science fiction but for some edgy-but-mainstream books (which he differentiates by going as Iain Banks, without the middle initial), and the writing here is at a high level, but this is definitely not a case of a "literary" writer slumming in sci-fi and just throwing a few spaceships and alien planets into the mix. The story has quite a bit of action and violence, and covers a very broad swath of space. In the "Culture" series, at least at the beginning, there's a war between The Culture (a very advanced race, or collective of races, who rely on powerful artificial minds to make live in the Culture one of utopic leisure) and the Idirans, which are a strange race of very large, shell-covered, three-legged beings who don't age (but can be killed). The war arose due to the Idirans expansion or empire-building (driven by religious fanatacism), which the Culture determined to stop. Though the author makes clear which side he believes to be morally justified, and his dislike for religion comes through pretty clearly, the main character (a member of a shape-changing race) is actually working for the Idirans.
The novel has a few flat spots, and there were times I set it down and didn't pick it back up for several weeks. Overall, though, the story's world is compelling and its scope is truly impressive. I look forward to taking the next several steps in this series, especially as I understand the second book, The Use of Weapons, to be considered the best installment.