There's six big stories about space empires in here. Five of the authors (Peter Hamilton, Neal Asher, Alastair Reynolds, Stephen Baxter, Ian McDonald) are British and Robert Reed is American. The stories from Hamilton (Confederation), Reed (Great Ship), and Baxter (Xeelee) are written for existing series.
I generally think of SF as having two directions: ideas, where the author has come us with science-like ideas and hangs characters and spaces onto them; and stories, where the author comes up with the narrative and then adds science. I found Ian McDonald's "Tear," which is nominated for Hugo, to be strongly idea-related and I liked it the least. On the other hand, I haven't read Peter Hamilton since Night's Dawn because I didn't like it, but I liked his "The Demon Trap" best. I liked the other four as well.
I recommend this book for those who like space opera and war.