In the 1970s, thousands of young gay men flocked to San Francisco. Mark Abramson, author of the best-selling "Beach Reading" mystery series and the AIDS memoir "For My Brothers," was one of them. In a time and place where sex was free, drugs were cheap, and the driving disco beat felt like it would go on forever, he landed in the great gay Mecca fresh out of college, reconnected with his old friend, the writer John Preston and soon encountered such...