Prefferably not ancient authours. Emperors like Caligula ans/or Nero. Been reading Goldsworthy's biography of Augustus and was looking for a book similar to that about other emperors or known romans.
I can recommend Aloys Winterling's Caligula: A Biography. I read it along with Suetonius' The Lives of the Twelve Caesars, but if you don't want to read ancient authors then just stick with Winterling