Oh dear, the creatively challenged suits and corporate lawyers at Games Workshop are making themselves look foolish again.
Apparently, they have forced a book off Amazon for infringing their trademark "Space Marine". The book in question is Spots the Space Marine by MCA Hogarth. Do they own the words space and marine when put together? It depends. They own the right to produce miniatures under that name and other related specific uses.
But it is ridiculous to suggest that no one can use those words for a story title. Observe above. This was published in 1936, and it is a sequel to Captain Brinks and the Space Marines, published in 1932. There are later uses of the words by other authors.
The term "Space Marine" has also been used in: books by Robert Heinlein, who invented the armoured space soldier: Star Troopers, and John Ringo; Games like Doom, Quake, Timesplitters, Eat Lead, Alien Storm, and Freefall Tournament; and the film Starblazers.
Dr Who had Marine Space Corps back in '73: Death of the Daleks.
Using their economic muscle to bully some poor little web author like this makes GW look not only stupid but also bullying.