You can find quite a few
details here.
Basically, what is going on is that Games Workshop, now that they're publishing e-books, has decided that they own the term Space Marine outside of gaming.
Of course, rather than going after books that are published by big six publishers, they're going after small time, self published authors who can't really defend themselves financially.
I don't know what they're thinking. I mean, there is absolutely no way that a self published book is going to be impacting their sales in any way. And if this does go to court, they could easily end up losing their trademark (because, lets face it, a term that's been in science fiction since the 1930s is going to be a generic term- especially since other people still use it generically).
What does everyone here think?