This book starts well, the setting is different than usual. There is some mystery about what the Americans did on the Moon, two countries are racing to land near an ancient American base. Then we have the ancient portal system and two old alien races that tried to use it. Still very good.
And then the protagonists starts to jump around via the portal system. After the third jump I started having difficulties with the story that goes metaphysical and looses all elements of the hard sci-fi that I like. And I really didn't see the point of the protagonists getting naked all the time and looking at one another's genitals. Perhaps it is a side effect of jumping between parallel universes ? ( )