Consider Phlebas is a space opera novel by Scottish writer Iain M. Banks, first published in 1987.
The novel revolves around the Idiran-Culture War, and Banks plays on that theme by presenting various microcosms of that conflict. Perhaps surprisingly, especially since this is the first (published) Culture novel, its protagonist Bora Horza Gobuchul is actually an enemy of the Culture.
It takes its title from a line in T. S. Eliot's poem The Waste Land. Look to Windward (2000), whose title comes from the previous line of the same poem, can be considered a loose follow-up.
The book was generally very well-received as a fast-paced space opera with a morally ambiguous hero and lots of grand scenery and devices, some original to the genre with Banks, some borrowed from other authors: the Orbitals for example show the influence of Larry Niven.
Probably the best Culture book to serve as an introduction to the fictional utopia. The Player of Games is sometimes suggested as being easier to read.
Banks said in an interview:
There's a big war going on in Consider Phlebas, and various individuals and groups manage to influence its outcome. But even being able to do that doesn't ultimately change things very much. At the book's end, I have a section pointing this out by telling what happened after the war, which was an attempt to pose the question, 'What was it all for?' I guess this approach has to do with my reacting to the cliché of SF's 'lone protagonist.' You know, this idea that a single individual can determine the direction of entire civilizations. It's very, very hard for a lone person to do that. And it sets you thinking what difference, if any, it would have made if Jesus Christ, or Karl Marx or Charles Darwin had never been. We just don't know.
Related: Look to Windward
Wikipedia, Iain Banks Net,