The City of Angels’ unholy underbelly has provided Walter Mosley with twisting plots and a wealth of fascinating and often shadowy characters.
  But the declarative sentence that started the best-selling author on his literary career had nothing to do with his hometown.
“A lot of people will tell you they knew they wanted to be a writer from the time they were 10 or 12 years old,” Mosley said during a recent telephone interview from Los Angeles. “For me, I was in my 30s before it ever became clear that that was something I would want to do.