"think it would be a better novel if Haldeman wasn't obsessed with group sex (he seems to put this in all his books Roll Eyes)."
What's wrong with group sex? Good fun.........

You want pervy, try late Heinlein..
I've recently finished "Judge" by Karen Traviss, this is the last of her 6 book Wess'har series. The Eqbas fleet has reached Earth, to judge & punish those responsible for a nuclear incident on the planet Bezer'ej, which nearly resulted in the extinction of the intelligent, aquatic natives. Once this minor matter is attended to, they will restore Earth's ecology to a balanced state, and repopulate it with many of the extinct species sent into space in a gene bank over a century ago. This will involve a forced reduction in the human population from 7 billion to 1 billion..... Intelligent, enjoyable SF, with a greenish tinge.
Also just re-read Alistair Reynolds "Century Rain", half Chandleresque detective story set in Paris, half wormholes, nanotech & a devastated Earth. Not as bleak as his "Revelation Space" series, and a decent ending (something I don't think he's good at)