This is a review for the first book of the Exodus series written by Doug Dandridge.
Empires at War comes across as an ambitious project. There is a huge number of characters, locations, and plot lines. Normally this is something that I like (for example, I think the Nights Dawn triology from Peter Hamilton is fantastic), but in this case I have the feeling that too much has been compressed into a single book (of just 384 pages). Essentially, this book feels like an introduction to the universe in which the story is going to unroll in later books (which I haven't yet read), but on its own this book has little to offer. There are simply too many characters and locations to keep track of, and the author switches between them too quickly (sometimes from one paragraph to the next). Since the locations are light-years apart the book requires you to keep in mind what information has made it to a given location. I'm not yet sure if I like this as a general approach, but in this specific case it did not work well because at least I wasn't able to keep all this information in my head. Often, I had to deduce from the behavior of the characters how far the plot had progressed ("ok, these guys don't feel nervous about an unknown ship approaching, so they must be at a point where it is not yet known that humanity is under attack").
On the plus side, the individual characters are done well (to the extent one can tell from the amount of space that they get), and the plot promises to be interesting. But on the other hand, none of the characters get a chance to really affect the plot and the plot does not evolve at all. This book does not have an end, it simply stops at a point where you'd normally expect a new chapter (or even a new paragraph) to start.
I believe most of the points above could have been easily avoided by merging this book with the next one (or maybe two) in the series, and delaying the introduction of some of the characters and locations to a later point. However, this is just speculation: I haven't read the other books yet.
On a different note, the plot also contains some elements that I'd normally not expect in a science fiction setting. For example, the emperor's bloodline has the ability to see visions of the future in their dreams. While there is nothing wrong with the idea per se, I found it discordant in this setting.
Another thing that really nagged me (though I don't hold it against the book) is the author's frequently repeated assertion that "humanity used to be technology 2000 years behind [their main enemy], but they caught up in just 500 years". This is so wrong that I cannot resist pointing it out here. The very definition of being x years behind is that it will take you x years to catch up -- if you do it faster then quite obviously you weren't behind that much to begin with.
Verdict: as part of a series this book might be a good read if you don't mind the mystical aspects. However, on its own (and it is sold as such), I don't recommend it.