A LOT of hard science and a LOT of detail at times that slows the plot, which is actually rather exciting. A fully human man in a spacesuit found on the moon turns out to be 50,000 years old. Further, he's from a planet, that no longer exists, that harbored fully human individuals and was beyond the orbit of Mars, called Minerva. It broke up due to the war that stranded this fellow on the moon and formed the asteroid belt, pluto, and depositied tons of debris on the farside of the moon, which also dates back to 50,000 years.
Intrigued? I sure was. I just ordered the forth book in the series and found out that the fifth is out in hardback, to give you an idea of how much I like this guy's way of thinking.