Sorry I thought you meant 2 more as in Addition to the trilogy
The Void series of books does take place in the same universe a bit later in the timeline, and does features some of the same characters. It is also three monster volumes of a thousand pages each.
It's not quite the same though, as the story alternates with the modern, Commonwealth characters and universe, and an alternate timeline in a pocket/alternate universe where instead of technology, society is pretty much based around mental/psionic powers. If you want a hard SF story, these fantasy-esqe parts will annoy you.
There are also several short stories set in the same Commonwealth universe, and a standalone book "Misspent Youth" that is well before the Night's Dawn books.
There are apparently two new Commonwealth books coming, set between the Night's Dawn and Void trilogies:
Wikipedia said:
Hamilton announced in 2011 that he is developing a new trilogy. He later cut this down to two books titled The Chronicle of the Fallers. It is a return to his Commonwealth Universe, set in the time before the Void Trilogy, and will tell the story of Nigel Sheldon and what happened when he broke into the Void. The first book will be ready for publication in 2014. Preliminary titles for the two books are The Abyss Beyond Dreams and The Night Without Stars.
I do like Hamilton, but I feel he's faded a bit in recent years, or maybe been eclipsed by the likes of Richard Morgan. Hamilton does a lot of two dimensional characters (he's especially bad at women), and does resort to deus ex machina far too often to pull a quick wrap-up of the end of the story.
His recent book "Great North Road" was very clever in places, but it was also slow, poorly paced, with a cliched ending and twist that was obvious from a mile away. It seemed that the first three quarters of the book was nothing but a long setup for the last quarter, which was rushed.
Hamilton's earlier, shorter books like the Mindstar series shows a sharpness and pace that seem to have been lost as he's indulged himself with ever longer novels.