Of course, this is Unauthorized - and  Allegedly! 

Both stars in question are DEAD.   A new book ‘ Hollywood Babylon Strikes Again!: More Exhibitions! More Sex! More Sin! More Scandals Unfit to Print ’, by Darwin Porter and Danforth Prince,  digs thru dark and trashy secrets  to expose some of the rumors and myths about long-dead superstars.

The authors dug up an old interview made with the late gay porn star Cal Culver (aka Casey Donovan)  conducted before his death in 1987, which sensationally claimed that he had an affair with Superman star Christopher Reeve, and gave details of their relationship. Culver, who died of an Aids-related illness, alleges that he met Reeve when they were both auditioning for a Broadway role in the mid-1970s. In the book extract, obtained by the Globe newspaper, Culver claims Superman star Reeve was ‘the man of my dreams’ and says that the pair had a passionate two-month relationship until Reeve discovered Culver was a gay porn star, performing under the name Casey Donovan.

He wrote: ‘Christopher was a great lover and I think I liberated him sexually. I didn’t think he was gay but he seemed willing to try anything once. He was curious.’

Darwin Porter, who co-wrote the book, said: ‘I have no doubt this was legit – I knew Cal for years and at one stage we even lived next to each other. He was a very credible source and all the other stories he has told me checked out.

Hmmmmmmm.  We'll  never know.