Generally, I re-read all previous books in a series when I buy the next book. This means I've read The Dreaming Void three times. I like it as much now as I did the first time, but I find it just as complex.
The Dreaming Void takes place millennia after two other books (Pandora's Star, Judas Unchained) that I have not read. That backstory gives the book depth, but also sometimes leaves the reader keenly aware that he is not part of the inner circle. There's nothing technically wrong with Hamilton's 'historical' references - they're not essential to the story, and he's generally careful to provide what is important in a digestible form. But the sheer number of 'inside' comments becomes a bit wearing, and makes a substantially complex plot even harder to follow. It's not always clear what is decorative and what is substance, as supposedly historical figures reappear from right and left
I'm sorry to say that even on a third reading, I didn't recall who all the factions were - on every run through the book, there were simply too many to keep track of, and I let them float by as narrative scenery ("complex politics, got it. Next."). That works pretty well. You don't have to remember the detailed differences between Highers, Advancers, Dreamers, and the ANA in general, because Hamilton does a very good job of keeping the actual foreground actors clear. I found I enjoyed the action even without making much effort to penetrate the presented mystery of who was secretly supporting whom.
The deep background works better with the many alien races presented - they're interesting, and here it's a pleasure to know that there's more to be explored if I choose. I probably will. It seems likely, for example, that the earlier books provide more information about the Sylfen - apparently a race of high-tech elves. As a writer, I'm curious as to whether they triggered Hamilton's desire to mix fantasy and SF.
That's really what this book is about - it presents a hard, high-tech, political science fiction environment interleaved with what's essentially a light steampunk story. The overall narrative is about how the two connect, and it works surprisingly well. I've only previously read Hamilton's SF (as far as I know, that's all he's written), but he has a remarkably deft touch with fantasy. While I liked the whole book, I much preferred the steampunk-y bits to the epic space opera sections. They definitely leavened the heavy SF politics of the main book. In essence, in fact, the fantasy bits had the same effect on me as they do on the characters of the SF universe - they left me wanting more.
Overall, then, a very satisfying read that sent me right out for the next book. If it's a bit complex keeping apart the factions, the Waterwalker, the Skylords, the Starflyer, etc, it's also a lot of fun following some very believable characters meeting interesting challenges.