Matter is one of the Iain M. Banks Culture novels. As with the others I've read, I enjoyed this one. He was a brilliant author and is sorely missed. You can read an excerpt from this book here.
synopsis from the book:
In a world renowned even within a galaxy full of wonders, a crime within a war. For one man it means a desperate flight and a search for the one -maybe two- people who could clear his name. For his brother it means a life lived under constant threat of treachery and murder. And for their sister, even without knowing the full truth, it means returning to a place she'd thought abandoned forever.SF Signal gives it 4 out of 5 stars and concludes, "Is Matter the best Culture novel by Banks? No, that’s still Use of Weapons. However, Matter can sit comfortably alongside Consider Phlebas for second." The review at SF Site calls it "a highly satisfactory romp". SFF World says, "the book shows Banks’ clear skills as an SF writer and many of the trademarks much beloved by Banks’ fans." Strange Horizons closes with this: "Relax, take nothing too seriously, enjoy the nifty weapons, the skilful writing and the stupendous scenery. Matter is good value, though it may not be the master’s best work." io9 says, "you'll love every minute of it."
But the sister is not what she once was; Djan Seriy Anaplian has changed almost beyond recognition to become an agent of the Culture's Special Circumstances section, charged with high-level interference in civilizations throughout the greater galaxy.
Concealing her new identity -and her particular set of abilities- might be a dangerous strategy, however. In the world to which Anaplian returns, nothing is quite as it seems; and determining the appropriate level of interference in someone else's war is never a simple matter.