Games Workshop (UK) is the purported owner of United States trademarks "Space Marines" in International Class 28 (No. 1922180, "board games, parlor games, war games, hobby games, toy models and miniatures of buildings, scenery, figures, automobiles, vehicles, planes, trains and card games and paint, sold therewith") and International Class 9 (No. 2100767, "video computer games; computer software for playing games"). (I'd offer links to the TESS entries, but TESS is based on session cookies.) MCA Hogarth1 wrote a piece of fiction that included Space Marines in the title, and sold it at the Big Brazilian River. GW issued a cease-and-desist letter, asserting its trademark rights.
There's just one tiny problem with GW's position: Books (and e-books) are not in International Class 28, and although e-books could call International Class 9 a home, they are not "video computer games [or] computer software for playing games," the limits of the US registrations. GW also claims a UK registration for "printed material" based upon stationery bearing the words "Space Marines", but that kind of extension within Class 16 (and Class 41) is explicitly not the law in the US. Too, this was at most an exemplary use — which is to say that it's the trademark equivalent of "fair use." And it goes that far if, and only if, Hogarth's novel uses "Space Marines" to refer to the Warhammer 40,000 variety of Space Marines.